Etymology

Proper noun

1. .
   • 1994, Floyd Skloot, Summer Blue, Story Line Press, ISBN 0934257086, page 98:

     "Just Jill, I'm afraid." "Would you prefer if it was Gillian?" "Oh, I think so. Gillian sounds so much fancier." "Fancy?" Terrence said. He smiled at her. "Or perhaps it sounds flashy?" "Royal," Richard said. "Flowery," Terrence added. "You could say Gillian was more flowery. That would fit. What about you, Corrie, what does it sound like to you?" "Rich," Corrie glanced at Jill. "Gillian sounds richer than Jill."

2. Generic use for any female (as Sheila in Australian English), especially paired (since the 15th c., compare Ienken and Iulyan) with the male Jack.
   • 1590, William Shakespeare, Love's Labour's Lost, Act V, Scene II:

     Our wooing doth not end like an old play;

     Jack hath not Jill; these ladies' courtesy

     Might well have made our sport a comedy.

3. 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').
4. A man's right hand; .
5. A jillstrap: the female counterpart to a jockstrap.