Green’s Dictionary of Slang

the vagina.

1732-1820		Order of the Beggar's Benison and Merryland (1892) 31: Dinner Sentiments [...] An Archangel could not but feel his Sinews stiffened with fierce desire to be suffocated within the yawning Chasm.
1980		Maledicta IV:2 (Winter) 182: The simplest words in common use for this ‘nasty thing’ [...] are those accepting the female sexual apparatus as a simple receptacle. These include [...] chasm, gap, gape.
2005		D. Jenkins Slim & None 67: ‘[The female organ that was known in my carefree college days as the blissful chasm’.