“I CAN HAZ AMERICA?” went the caption on a photo of a wide-eyed Sarah Palin that circulated on the Internet soon after John McCain chose the Alaska governor to be his running mate. A few years ago, the caption would have been incomprehensible. But today almost any Web logger in America could tell you that the reference is to lolcats, the ironically cutesy, “laugh-out-loud” photos of cats on top of which deliberately misspelled captions are superimposed. Traditionally the cat in such photos asks for a cheeseburger. So popular have lolcats become that there is now a wiki — a collaboratively written set of Web pages, so named after the Hawaiian wiki-wiki, which means “quick” — where the Bible is being translated into their dialect.

The words lolcat and wiki are among the newest in the English language, so new that lolcat doesn’t appear in “The Secret Life of Words” (Farrar, Straus and Giroux, 440 pages, $27), Henry Hitchings’s account of the growth of English vocabulary over the centuries, though wiki does. According to Mr. Hitchings, there were 50,000 words in the English language a millennium ago, and there are at least 700,000 today. Half of English words are borrowed, some from the jargon of subcultures such as the Internet, but more often from other languages.

“Borrowings have a ‘psychological climate,'” Mr. Hitchings writes, himself borrowing a phrase from a scholar of loanwords. Therefore, Hitchings continues, “we can use details of language to open up a historical vista.” For example, in the 1842 coining of dinosaur, which was composed by joining the ancient Greek words for “scary” and “lizard,” one can see the pride in the ability to read Homer in the original that was typical of 19th-century intellectuals, even those who dug up bones for a living. And in the emergence of the word teenager in the 1940s and 1950s, one can sense the optimism, informal style, and sociological self-regard of America just after World War II.

Some loanwords look foreign, while others pass among us undetected. It is hard to overlook the Japanese origin of tsunami, which made landfall in 1897. Monsoon sounds so alien that it’s no surprise to learn that it comes from Portuguese traders, who passed it on as they rubbed shoulders with the English while in India. But almost nothing about hurricane suggests to a casual speaker that the word comes from Spanish. In general, the rule seems to be that the older a borrowing is, the less foreign it sounds. The word street, for example, came from Latin while Germanic tribes were still fighting for turf in the British isles, whereas status quo was taken from the same language by learned Victorians, a millennium and a half later. The French language loaned the word scandal to English as early as 1230, and it now sounds as English as bangers and mash and as American as moose sausage, but the still very French-sounding ancien régime seems to have been popularized in English by translations of Tocqueville, who wrote in the 19th century.

A word’s origin affects its connotation. As the oldest element and the core of the language, “the Anglo-Saxon part of the English vocabulary seems to earth us,” Mr. Hitchings writes. As an example, he notes that the Anglo-Saxon go is familiar and powerful; the French-derived depart is formal and more effete, and the Latin exit “suggests something more specialized or technical.” For centuries, reformers have wished to strengthen English by purging it of polysyllabic French and Latin immigrants. Samuel Johnson, for one, barred finesse from his famous dictionary as “an unnecessary word.” (Though he did give an entry visa to escargatoire, “a nursery of snails.”) Mr. Hitchings shows such efforts to be more or less eccentric and inevitably doomed, and suggests that if by some miracle they were to succeed, they would needlessly deprive English of its distinctive multilayered texture. In an intriguing wrinkle, it transpires that English has borrowed so prodigally that sometimes it has borrowed the same word more than once. A single Scandinavian root gave English both shirt and skirt. And when, during the English Renaissance, the Latin-derived conceit began to imply intellectual arrogance, the underlying word was borrowed from Latin anew, to form the more neutral concept.

The bulk of Mr. Hitchings’s book consists of a galloping history of English-speaking people and lists of words they have borrowed or invented. The prose is heavy with these lists, and the connection between one list and the next is sometimes vague. Every dozen pages or so, the reader may find that his mind is involuntarily shutting down to clear its RAM buffers of excess data. In smaller page-doses, however, the lists are pleasant and amusing.

Celts invaded the British Isles millennia ago. After a few centuries of Roman rule, which ended in 410 C.E., tribes of Angles, Saxons, Jutes, and Frisians came pillaging. The tribes must have been abetted by a superhuman force — perhaps a plague or a climate catastrophe — because their Germanic languages drove out the Celts’ Brittonic ones almost completely. Another group, the Vikings, began attacking from the north and east in 789 C.E., and the Vikings’ language, Norse, merged in time with Germanic tribes’ Anglo-Saxon. Perhaps because the Norse and the Anglo-Saxons despaired of learning one another’s word endings, the language they forged together had very few and instead defined the grammatical role of words by the order they appeared in. Anglo-Saxon bequeathed the most common words in English today — the, that, of, from, in, by, to, with, and and. Norse gave us loose, weak, scare; such nautical terms as storm and sea, and such metaphorically nautical phrases as clear the decks, second-rate, and show one’s colors. In 1066, when the Normans won the Battle of Hastings, their French-speaking aristocracy replaced the Anglo-Saxon-speaking one, and French became the source of words for war (siege, armor), morality (courtesy, courage), fashion (ermine, style), and law (jury, crime

). By the 14th century, however, the Norman-descended kings were speaking the English of their subjects. The language achieved a certain glamour (a Scots word, from grammar) in the hands of writers such as Chaucer (responsible for ambassador and intellect) and Bible translators such as John Wyclif (puberty, zeal) and William Tyndale (beautiful, scapegoat). After America was discovered, sailors brought home such new words as Eskimo, Abenaki for “eaters of raw flesh,” and avocado, Nahuatl for “testicle,” a shape the fruit resembles. With the advent of the Renaissance, French jetted forth yet again, imparting perfume, mediocre, and naïf, while Italian gave carnival, disgrace, and balcony. It was a fertile era; Mr. Hitchings reports that the works of Shakespeare “contain our first sightings of some 1,700 words.” In the 17th century, when wars of religion erupted, English speakers learned to distinguish carefully between what was a matter of fact and what was mere opinion, and the high-living Samuel Pepys introduced the phrase have a good time. In the 18th century, which saw the birth of charming and low-bred, the novelist Fanny Burney described a character as grumpy, and the novelist Laurence Sterne described another as good-tempered. And on Mr. Hitchings goes, until Hemingway borrows cojones from Spanish and the British borrow nark from the Gypsies to describe someone who finks to the police.

The 20th-century food writer Elizabeth David, Mr. Hitchings has discovered, was single-handedly responsible introducing into English the words bruschetta, taleggio, and salade Niçoise. Alas, not long after announcing this discovery, Mr. Hitchings is sent over the edge by the etymology of cappuccino and wanders unhappily into diffuse social criticism, regretting consumerism, cell phones, and the violent language often used to describe male sexuality. “Life insurance is really death insurance, after all,” he writes, a truth that no one needs to be told, but he’s had an exhausting tour through the linguistic databases, and he deserves to nap through the last dozen pages if he needs to. It isn’t fair to end on such a note, so in a desultory fashion more appropriate to the book, here’s a different one: Mr. Hitchings reports that the bikini was named in a 1946 marketing stunt for a South Pacific atoll ruined by an atom bomb a few days before a line of swimwear’s debut.

Mr. Crain is the author of “American Sympathy: Men, Friendship, and Literature in the New Nation” and has written for the New Yorker, the New York Review of Books, and n+1.