Green’s Dictionary of Slang

the female pubic hair.

1659		Mercurius Democritus 20-27 July 79: They come to Sluts Well, scituated in a Mossey Valley betyween two Hams.
1772		G. Stevens ‘Administration’ in Songs Comic and Satyrical 155: On the Hill, along the Dale, / I sometimes turn a Rover, / Then within the Mossy Vale / I slily creep to Cover.
1836		‘Rural Felicity!’ in Comic Songster and Gentleman’s Private Cabinet 27: The sweet mossy cave is my pride.
1857		Venus’ Miscellany (NY) 23 May n.p.: The mossy tuft tho’ thick it grew / Could not conceal the glowing hue, / Of rich vermillion.
1883		‘Three Chums’ in Boudoir I 7: His left hand found no resistance in its voyage of discovery under her clothes. What mossy treasures his fingers searched out.
1890–1904		Farmer & Henley Sl. and Its Analogues IV 339: Mossy bank [...] mossy-face.

the female genital area.

1857		Venus’ Miscellany (NY) 31 Jan. n.p.: Here is to the hoary-headed hermit, who never enters his mossy cell without dropping a tear.
1890–1904		Farmer & Henley Sl. and Its Analogues.

(US) the vagina.

1988

(con. WWII) S. Hynes Flights of Passage 44: The female organ was ‘the bearded clam’ or ‘the mossy doughnut’.

the female genitals and pubic hair.

c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Mossy-face, the monosyllable.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn) n.p.: Mossy Face. The mother of all saints.
1811		Lex. Balatronicum [as cit. 1788].
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue [as cit. 1788].
1890–1904		Farmer & Henley Sl. and Its Analogues.

see moss-back n. (1)