Jill

Jill is a short form of the forename Gillian. There are two main types of such shortenings: they are convenient for writing, e.g. in lists; or they are essentially spoken pet-names, and thus informal. (See Conventional abbreviations for forenames.)

Short form	Long form	Informal or written	Other short forms	Remarks
Jill	Gillian	informal	Gill	Jill is nowadays usually an independent name, but began as a shortening

There is a list of similar names at Conventional abbreviations for forenames, as well as the category:short names

Note that any informal form may be spelled in different ways. Notably, any spelling listed that ends in '-ie' may be written with the ending '-y', and vice versa.

See also gill (disambiguation) for other uses of the word

Jill (or Gill) was a stereotypical name for a woman, often coupled with Jack as in the nursery rhyme

Jack and Jill

Went up the hill

To fetch a pail of water;

Jack fell down

And broke his crown,

And Jill came tumbling after.

and an old proverb, "Every Jack has his Jill". The compound "Jill-of-all-trades" has even been used, although the masculine equivalent "Jack of all trades" is more usual.