2000s
pads without panty lines? the thong pad invented
Thongs weren't always a common choice for everyday underwear. In fact, it wasn't until the 1990s that some women started wearing thongs under their clothes regularly. Because thong underwear doesn't allow much fabric for regular pads to stay in place, manufacturers started producing pads and panty liners in the early 2000s with a tapered shape to fit in the crotch of a thong.
Some girls find that thong pads and panty liners don't offer as much protection because of their shape, while others find them handy when their period is light or use them as added protection in conjunction with tampons.