thong [OE] Thong is related to twinge [OE], which originally meant to pinch. In Anglo-Saxon times a thong was a shoelace. It then came to be used for any narrow strip of leather, and finally to any thin strip of material, from which came the modern use for minuscule underwear in the 1970s, but from the 1960s a term in Australia and the US for a flip-flop sandal, which can lead to confusion.