(n) :
generic use for any female (as
Sheila in Australian English), especially paired (since the 15th c., compare Ienken and Iulyan) with the male Jack; also in the compound
jillstrap (also shortened as jill), the female counterpart of a
jockstrap; a young
woman; a
sweetheart; like the variant spelling Gill it was also associated with various assertive uses of the term flirt, as in flirtgigg (used by William Shakespeare for a 'woman of light or loose behavior')