"mort" (woman)

[Jonathon Green]

Mot is etymologised in the OED as no more than an alternative sp. and chronological successor to mort and the two words share an entry. Other suggestions have been the Dutch mot, a woman (Barrere & Leland, who call it 'old Dutch slang') and (surely less feasible) French amourette, a girlfriend. Its first published use seems to be in Captain Grose's Classical Dict.of the Vulgar Tongue (1785), 'Mot: a girl or wench. See mort.' Whether there is a real link betw. mort/mot is by no means proven. Other than in consciously archaic uses by Walter Scott and Ainsworth, both writing historical novels, and a wholly anachronistic apparance in James Curtis' Gilt Kid (1936) mort had pretty much vanished by mid-18C. 
I quote (and agree with) Gordon Williams Dict. of Sexual Language & Imagery in Shakespearian & Stuart Lit.' (1994; vol II p.911):

Mot is found is most collections of C19 flash lingo; Barrere and Leland are probably to be relied on in tracing it to old Dutch slang mot, whore, since there is no evidence of mort's continuity. They have 'mot-cart', mattress, and F[armer] & H[enley] have 'motting', wenching. Their 'mot-carpet' = woman's pubis derives from 'motte', hillock, which is similarly used.

The fact that modern Dubliners use mot does not, I would suggest, have any bearing on the Irishness or otherwise of mort.

Jonathon Green