The verb lam has two meanings: to hit or to run away. If you see a bully making little kids cry, you may be tempted to lam him in the nose and then lam before he can retaliate.
The British slang meaning of lam, "hit or beat," is the oldest one, dating from the 16th century. It stems from an Old Norse root that means "to beat" or "to make lame." The newer, North American definition, "escape," can also be used as a noun: "After he stole his cousin's car he went on the lam." Experts trace this meaning back to slang used by pickpockets.