“Call me mint jelly, because I’m on the lam!”

The fact that there’s no B at the end of that particular lam suggests that the origin of "being on the lam"—that is, on the run from the law—doesn’t lie down on the farm. So where does this bizarre expression come from?

The phrase on the lam first emerged in the late 19th century as to do a lam, a slang expression defined in an 1897 article in Popular Science as simply “to run.” (Alongside it, we’re told Victorian criminals were already taking kips when they fell asleep, were rubbernecking when listening in on others’ conversations, and would give longwinded spiels instead of speeches). But by the turn of the century, to do a lam had morphed into to go on the lam, which first began to crop up in print in the early 1900s and has remained unchanged ever since.

As a verb in its own right, however, lam dates back as far as the late 16th century. The Oxford English Dictionary has unearthed it in a dictionary compiled in the mid-1590s (alongside a long-lost equivalent form, belam), but back then the word’s meaning was considerably different: in 16th century English, to lam meant “to beat” or “to thrash someone harshly.”

In that sense, lam is probably a distant cousin of lame (and so might have originally implied beating someone to the point of injury) and actually still survives in the word lambaste, which today means "to scold" or "castigate," but back in the 17th century also meant "to beat." Precisely where the word came from before then, however, is a mystery, but it’s possible that lam has Scandinavian ancestors and could be descended from an Old Norse word, lemja, meaning “to beat” or “strike.” But no matter what its earliest origins might be, how did we get from beating someone to running away from the law?

Lam survived in this original sense until the 19th century when, having steadily fallen out of everyday use, it began to crop up in the schoolyard slang of British (and later American) schoolchildren. By the mid-1800s, lamming out or lamming into someone was being widely used in reference to schoolyard fights and scuffles, and it’s perhaps through association with schoolboys running away before they were caught fighting by their teachers (or else, with the hapless victim running away before the first blow was thrown) that lamming finally came to be used to mean “to escape” or “to abscond.”

In this sense, lam first appeared in print on its own in 1886, in Allan Pinkerton’s memoir Thirty Years A Detective. In it, Pinkerton—the Scotland-born founder of Chicago’s renowned Pinkerton National Detective Agency—describes in detail the precise operations of a pickpocketing gang:

"After selecting their victim or 'mark,' who is engaged in drawing a large sum of money from the bank, one of the number will take up his position inside the bank, where he can watch every movement of the man who is to be robbed … Quick as a flash, and yet with an ease of motion that attracts no particular attention, the 'tool' turns sideways, almost facing the man, but upon his right side. The 'tool' usually carries a coat upon his arm for the purpose of covering his hand; with the concealed hand he will work under the man’s coat, and taking the wallet or package by the top, will raise it straight up, until it is entirely clear of the pocket; then drawing it under his own coat, the robbery is complete … If he is rather slow about getting to the wallet or the money and he notices that the front men [two other members of the same gang] are getting somewhat uneasy, he calls out 'stick!' This means that in a few seconds he will be successful, and that they are to stay in their respective positions. After he has secured the wallet he will chirp like a bird, or will utter the word 'lam!' This means to let the man go, and to get out of the way as soon as possible. This word is also used in case the money cannot be taken, and further attempts are useless."

It’s from here that phrases like doing a lam eventually emerged in the later 1880s, and criminals have been going on the lam ever since.

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