Half a dozen graceful giraffe crossed in front of the safari vehicle. “That’s a kaleidoscope of giraffe,” the safari ranger said. “It’s also called a journey or a tower of giraffe.”

Most of us have heard of a “pride” of lions, a “school” of fish, a “herd” of buffaloes (or similar animals), and, of course, a “gaggle” of geese, but it seems that many other animals have their own collective nouns as well. Those terms can vary, depending on context and location.

Search Google for “collective nouns for animals,” and you’ll come up with all sorts of interesting results, some familiar and some not so much:

a congress, flange, tribe, troupe, or troop of baboons

a convocation or aerie of eagles

a herd, memory, or parade of elephant

a bloat, herd, or crash of hippos

a leap of leopards

a crash of rhinos

a herd, dazzle, or zeal of zebras

Which raises the question of why those terms exist, why some animals have more than one collective noun, and who made it that way.

The answer, or so it seems, is because.

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Many these collective nouns are often traced to a 1486 treatise called the Book of St. Albans, which includes a list, “The Compaynys of beestys and fowlys,” with many collective nouns for animals. Similar lists were compiled throughout the 15th and 16th centuries, usually under the guise of providing “proper” terms for gentlemen to use while hunting those beestys. (This is pure speculation, but perhaps it was a kind of gentry jargon: One could speak of going after a “sounder,” and the other gentry would know that the target was swine, without letting hoi polloi in on the secret.)

In an exhaustive piece in the Transactions of the Philological Society 1907-1910 (digitized by Google), a man named John Hodgkin examines many of these collective nouns for groups of animals, birds, and fishes in historical and etymological contexts. (Other groups are also included, including a “discretion of priests” and a “rascal of boys,” but we’re dealing just with animals here.) It’s entertaining though sometimes dense reading, if you can ignore or interpret the contemporary spellings.

Even though Hodgkin looked for these terms in contemporary dictionaries as a way to establish or dismiss their legitimacy, you won’t find many in modern dictionaries, which is a clue to just how informal they really are. Even when you can find one, the dictionaries often turn up their noses at them. The Oxford English Dictionary, for example, has a definition for “a murder of crows.” Its origin, the OED, says, is “uncertain,” “perhaps alluding to the crow’s traditional association with violent death.” Tracing its first usage to 1485, about St. Albans’ time, the OED defines a “murder of crows” as “One of many alleged group names found in late Middle English glossarial sources.” (Emphasis added.)

So it seems as if many of the collective nouns are fanciful inventions using the animals’ characteristics. It’s fun to think of a “sneak” of weasels, which evokes the slithery, furtive movements of the beestys, but calling a group of them “a group” or “a number” or even “a batch” is just as “correct.”

There’s another mystery, as well: Webster’s New World College Dictionary, the one preferred by the Associated Press and many other news organizations, says that the plural of “giraffe” is “giraffe” and the plural of “elephant” is “elephant.” But the plural of “lion” is “lions” and the plural of “leopard” is “leopards.” More than one “buffalo” is “buffaloes” (with “buffalo” and “buffalos” as alternate plurals), and more than one “zebra” is “zebras” or “zebra.” The plural of “fish” is “fish,” unless you’re dealing with different species, WNW says, in which case it’s “fishes.” More than one hippopotamus can be “hippopotamuses” or “hippopotami” or even “hippopotamus,” and the plural of “rhinoceros” is “rhinoceroses” or “rhinoceros.”

As with so many other things, there is no logic. Sometimes it depends on whether you are referring to the individuals or the group itself, but that’s too hard to remember. That’s why it’s easy to just call them “rhinos” or “hippos.” Just be sure to get out of their way.

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Merrill Perlman managed copy desks across the newsroom at the New York Times, where she worked for twenty-five years. Follow her on Twitter at @meperl.