a woman, especially a young woman; a flirtatious or sexually promiscuous woman; also, a prostitute ...1573 obs.
from the female name Gillian, from Anglo-Norman Giliane, a variant of Juliane, from classical Latin Iūliāna, from Iūlius, a Roman gentile name + -āna, feminine of -ānus -an
FIRST DOCUMENTED USE
1573 - see EXAMPLE below
"...Some horskeper, lasshith out prouender so,
some gillian spendall, so often doth go.
for hogs meate & hennes meate, for that & for this:
that corne is consumed, er chapman hath his...."
From: Fiue Hundreth Points of Good Husbandry Vnited to as many of Good Huswiferie first deuised, & nowe lately augemented with diuerse approued lessons concernng Hopps & Gardening, and other Needefull Matters
- Thomas Tusser