Green’s Dictionary of Slang

lam v.1

also lamb, lambo, lamm, lamme
[linked to ON lemja, to lame, as a result of a beating]

1. [late 16C+] to beat or strike; thus lambing/lamming n., a beating; lam out v., to lash out.

2. [mid–late 19C] (US) to defeat in a fight or sporting contest.

3. [late 19C] (Aus.) to swindle.

4. [1910s–40s] to throw, to toss, to smash against.

5. [1920s] in fig. use, to do perfunctorily, fast.

In phrases

give lamb and salad (v.) [pun]

[mid-19C–1900s] to beat, to thrash.

lam (it) into (v.) [the term began life as UK sl. but crossed the Atlantic to reappear in criminal milieux]

1. [late 19C+] to beat up.

2. [late 19C+] to do something aggressively, wholeheartedly.

3. [1970s+] to attack verbally.