It’s about time. We are now on Instagram!
Old English þwong "thong, narrow strip of leather (used as a cord, band, strip, etc.)," from Proto-Germanic *thwangaz (cf. Old Norse þvengr), from PIE root *twengh- "to press in on, to restrain." As a kind of sandal, first attested 1965; as a kind of bikini briefs, 1990.