catheads, n. — Green’s Dictionary of Slang

catheads n.

[SE cathead, a large biscuit eaten in the US; thus the breast’s roundness reflects that of the foodstuff; however, the term predates US use. Partridge (1984) cites 18C naut. jargon cathead, ‘a beam projecting almost horizontally at each side of the bows of a ship, for raising the anchor from the surface of the water to the deck without touching the bows, and for carrying the anchor on its stock-end when suspended outside the ship’s side’ (OED). But other than there being a pair of catheads, it is hard to see any more concrete a link]

the female breasts.

1811		Lex. Balatronicum.
1829		Vidocq Memoirs (trans. W. McGinn) II 24: She is the sister-in-law of our host [...] what catheads she has.
1842		Wkly Rake (NY) 12 Nov. n.p.: ‘His cut-water was just over her cat-heads’.
1844		Cork Examiner 14 June 2/6: I clapt my eyes on a snug craft sailing along under press of sail [...] My eyes! what catheads she had.
1896		Farmer Vocabula Amatoria (1966) 42: Bossoirs (les), m. The paps; ‘the cat-heads’.