"Twitch" doesn't hide any fancy spelling tricks or fake Latin dress-up job — it just comes from a long, straightforward line of Germanic words for pulling and pinching. Back around 1300, English had "twicchen," meaning to pull or yank something with a quick jerk. That in turn came from Old English "twiccian," meaning to pluck or grab hold of something, which traces back to an old Germanic root shared by relatives like Dutch "twikken" and German "zwicken," both meaning to pinch or tweak. Over time, the spelling smoothed out from "twicchen" into the "twitch" we use today — no silent letters or scholarly makeover involved, just centuries of English wearing down its edges into a simpler shape.
The meaning has also drifted a bit over the centuries. Originally it was about a deliberate action — someone tugging or yanking something sharply. By the 1590s, though, it had picked up a second, involuntary sense: the body moving or jerking on its own, spasmodically, without anyone meaning it to. As a noun, "twitch" showed up in the 1520s to describe a quick, sharp tug, and by 1718 it had also come to mean the small, spastic jerk of a muscle — the sense we mostly use now when we talk about an eye twitching or a nervous muscle spasm. So the word has quietly shifted from something you *do* to something that just *happens* to you.
twitch (v.) c. 1300, twicchen "pull or draw apart with a quick jerk," from Old English twiccian "to pluck, gather, catch hold of," from Proto-Germanic *twikjon- (source also of Low German twicken , Dutch twikken , Old High German gizwickan , German zwicken "to pinch, tweak"). Intransitive sense of "move or contract quickly or spasmodically" is by 1590s. Related: Twitched ; twitching . also from c. 1300 twitch (n.) 1520s, "short, sharp pull or tug," from twitch (v.). As "short, spastic contraction of the fibers of muscles" by 1718. also from 1520s