Take a bit of twill fabric and rub it between your fingers. It is not so smooth as satin, nor even as a plain weave; it is rough, it has ribs, it has traction. Whether it be cotton, or wool, or even silk, it grips. It does not shine, nor does it whiffle like corduroy as you ruffle it, but ’tis rugged and ready: ’twill serve. It is not a thrill from the mill, but it is twill.
How is it made? It starts one way but then skips ahead. Where in a plain weave your weft (cross thread) goes under your warp (long thread) and then over and then under and then over, in twill it goes under and then over and then over again, and sometimes again: a repeat, a three-peat, maybe even a four-peat. Sometimes it goes under more than once before going over. And the next thread is offset by one alternation, so that a diagonal pattern is formed.
Want to find some twill? Skip your suits and head to your jeans: denim is made with a twill weave. It’s not that twill is never used for formal wear – you’ll see some on the couture runways – but it’s more rugged and less prone to showing stains and smirches.
And the name, twill? So many names of fabrics come from places – denim is from serge de Nîmes, satin is from Zayton (the medieval Arabic name for Quanzhou), tulle is from Tulle. But twill comes from two places: Rome and England.
OK, I’m going diagonal; it’s obviously not a blend of those two place names. It’s just that it started as Latin bilix, from bis ‘twice’ and licium ‘thread’, but then it skipped ahead and turned that bi into two to make Old English twili, which became twilly, which became twill. (There was originally a thrili to go with twili, but it’s all just called twill now.) It’s sort of like how we went from repeat to three-peat – and then back to two-peat.
Two-peat? Yes, that’s in use; I wrote about it years ago. You are free to dislike it, but it is in use, especially among a set of people who wear twill more often than satin, and like it or not, it will serve. And if you will call twill twill, as one does, you have one less basis for objecting to word forms developing diagonally… as ’twere.