Gill

Gill.—The infernal river of Scandinavian mythology.
or jill , a homely woman; “Jack and Gill,” &c.
sb. a familiar term for a womanVariants: jillEtymology: Short for Gillian, a woman's name, Sh ; Latin Juliana
The abbreviation of Gillian, figuratively used for woman. Every jack has his gill; i.e. every jack has his gillian, or female mate.