Assumed to be old word (old for the under 30 crowd) describing a
flirtatious, possibly
promiscuous, girl; connotation leaning heavily toward flirtatious rather than
promiscuous.
Originates in the idea that a flirty girl in a skirt (think 50s era) could flip her skirt up quickly to give the guys a view of her panties, as a tease, but in an overtly sexual rather than playful manner.