A short form of Gillian, from Latin Juliana, the feminine of Julius, possibly meaning 'youthful'.
Jill is the breezy English short form of Jillian, itself a variant of Gillian, which derives from the Latin Juliana — feminine of Julius, the great Roman clan name possibly connected to Jupiter or to the Greek ioulos, meaning "downy-bearded," a poetic reference to youth and first growth. The name has been in English use since the Middle Ages, where Gill or Jill appeared as stock names in folk rhymes and comic verse representing the archetypal English girl: lively, practical, and unadorned. The most enduring cultural imprint comes from the nursery rhyme "Jack and Jill," which dates to at least the eighteenth century and has been interpreted variously as political allegory, astronomical reference (Jack and Jill as the craters on the moon Callisto), and simple comic verse about childhood misfortune.
This association gave Jill a quintessentially democratic, cheerful quality — the name of someone who climbs hills and gets back up again. Jill Ireland and Jill Biden brought it into mid-century and modern public life with different but complementary connotations of elegance and resilience. For decades Jill was a staple of American and British naming charts — peaking in the 1960s and 70s — before declining as parents sought more elaborate options.
Today it occupies a curious retro appeal: short, clean, and unfussy in an era of maximalist names, with a warmth that longer derivatives like Jillian lack. It is a name that wears well across an entire life.