You learn that someone you know has committed some sort of crime and is trying to dodge authorities: would you say they on the lam or lamb?
Lam or lamb? The answer to the question would likely seem to be lamb, since it’s a word people have actually heard of and seen often in print. Lam is the kind of word you hear from time to time, but rarely see written out.
But someone who’s on the run would probably have bad luck if they chose a lamb as a means of transport since they’re not the brightest animals in the world and probably wouldn’t get them anywhere all that quickly.
Yes, someone who’s on the run is “on the lam.”
The Online Etymology Dictionary tells us lam came to English in approximately 1886 as slang meaning “to run off.” The origin of the word is not clear, but they theorize that an alternate meaning of lam might explain it.
That alternate meaning, which dates back to the 1590s, is a verb that means “to thrash or beat.” Thus, someone who would lam someone could leave them lame.
It’s possible, the dictionary theorizes, that with lam meaning to beat, it could be connected to another slang expression, “to beat it,” as an association with running away.
That might be something of a stretch, or it might actually perfectly explain why we say someone who’s in hiding might be “on the lam.”