Events of this past week in Boston prompted me to look into the origins of an expression I heard quite often on the news: on the lam. Meaning to be a fugitive from the law, the etymology of this idiomatic expression is fairly murky although it is most often thought to be urban slang from the 1920s commonly in use by members of the criminal underworld. The Random House Historical Dictionary of American Slang traces it back to the mid-19th century, but it appears related to Old Norse lemja, meaning ‘to depart hastily’. H.L. Mencken thought its origins came from Elizabethan England, where it meant the same thing as beating it, an idiom still in use meaning ‘to run away’ and immortalized in a song by Michael Jackson. Its origins seems much less clear than vamoose, which appeared in the early 19th century and is derived from the Spanish vamos (let us go) — but this expression does not necessarily mean one is ‘running away from the law’, and conjures up images of grizzled 1840s gold prospectors rather than CNN.