You've probably heard of someone being "on the lam." Maybe a bank robber is on the lam after their latest heist, or maybe there's been a jailbreak and the escapees are on the lam. This American English idiom means "trying to avoid being caught by police," according to Merriam-Webster.
But wait – what is a "lam"? And why is anyone on it? Does it have anything to do with riding baby sheep away from a crime scene? All great questions, and there's not a perfectly clear answer. Though, sad to say, it does not have to do with using lambs as escape vehicles.
We do know that it was first used in the late 19th century. Allan Pinkerton, founder of the Pinkerton Detective Agency, wrote in 1900 that the word "lam" was first used by pickpockets to alert each other to danger:
So while the coppers may not have been on their tails yet, pickpockets were using the word "lam" as a signal to run away from potential trouble.
We also know that it was used in the phrase "do a lam" in 1897, meaning an escape or a getaway, according to "A Dictionary of the Underworld." From there, it evolved by 1904 to mean being a "lamster" or fugitive, and by 1932 it meant escaping from prison. It even made appearances in Appleton's Popular Science Monthly in 1897 and Damon Runyon's "Guys and Dolls" in 1931.
We can see where "lam" started and where it went, but where did it come from? It seems to have originated with the Old English word "lam," which meant "a beating." It's related to the beginning of the word "lambaste," which itself combines two words meaning "to beat or thrash," "lam" + "baste." This word means business.
There's another theory that the word comes from "lammas," which was also spelled "nammou" and was related to "vamoose," which is another slang word for "get the heck outta here." Given how slippery pronunciations may be, it's possible that these words are all connected.
But think about it: "lam" means "beat," and American slang also uses "beat it!" to mean "run away!" So it might make more sense for that Old English "lam" to be used in the same sense: to "beat a retreat," as we also sometimes say.