Green’s Dictionary of Slang

an unattractive woman, with whom one cannot achieve an erection.

1948		Sat. Rev. Lit. (US) 22 June 49/1: The ‘lumberjills,’ in gay plaid, represent a feminized form of the lumberjack.
1956		‘Charles Raven’ Und. Nights 153: I’m not qualified to lecture on the psychology of lumber-jills.
1999		Roger’s Profanisaurus 3 in Viz 98 Oct. 19: lumber-Jill n. A hatchet-faced woman that fells your wood.