by 1997, from up (adv.) + skirt (n.). As a verb by 2008.
"Upskirt" videos, usually taken using low-hanging bags, feature up-close-and-personal crotch shots of leggy, panty-clad young women. [Weekly World News, Sept. 29, 1998]
upset
upshot
upside
upside down
upsilon
upskirt
upstage
upstairs
upstanding
upstart
upstate
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