marrowbone and cleaver, n. — Green’s Dictionary of Slang

marrowbone and cleaver n.

[note Grose, 1785: ‘marrow bones and cleavers, principal instruments in the band of rough musick; these are generally performed on by butchers, on marriages, elections, riding skimmington, and other public, or joyous occasions’]

the penis.

[1654		Mercurius Fumigosus 26 22–30 Nov. 225: I mean such a Mary-bone that the Mary-bone man held in his hand when he was pissing against Hatton-Wall].
[1800		Sporting Mag. Apr. XVI 27/2: She was accompanied by the two Master Tripes, one on the marrowbone and cleaver].
1890–1904		Farmer & Henley Sl. and Its Analogues.
c.1904		A. Crowley Snowdrops from a Curate’s Garden 36: It was solid marrow-bone she wanted, and tons of it at that.

In phrases

look marrowbones and cleavers (v.)

(US) to stare aggressively.

1842

Flash (NY) 31 July n.p.: Liz Porter [...] sat mum and glum in a corner, looking marrow bones and cleavers at us.