This saying has word experts as befuddled as a bunch of zoo wardens trying to coax primates out of a large wooden container.

According to Phrases.org, Cassell’s Dictionary of Slang dates the phrase a “barrel-/wagon-load of monkeys” back to the late 19th century. But it doesn’t explain why a group of Industrial Age apes would be hiding in barrels or riding in farm carts.

Some sites have ventured theories. “Monkeys like to cram themselves into a large barrel at the circus,” the Daily Jolt offers, explaining, “This is probably the origin of the phrase.”

About.com quotes both the Oxford English Dictionary, which says the saying may come from “a barrel of laughs,” and word historian Charles E. Funk, who wrote: “One monkey arouses a great deal of amusement. Two or more then double the…amusement. If one were to release a barrelful…of monkeys, we must suppose that their antics would become hilariously comical.” We might.

Still on About.com, we followed the OED’s history of the phrase. It begins with a wagonload of monkeys, and includes mention of the mischievous beasts in cages (1840), bags (1908), and cartloads (1930). But it never reveals why humans started imagining them there in the first place — or why it would be fun.

Perhaps it’s the silliness of the image, or how perplexed and tickled you’d feel if you ever saw a barrel of monkeys. But for now, it seems, we’re left wondering how to help the little guys out, and never knowing exactly how they got in