twitch v.

c. 1400, erþe-worme, popular name of the worms of the family Lumbricidae, from earth + worm (n.). In this sense Old English had eorðmata, also regnwyrm, literally "rain-worm." Old English also had angel-twæcce "earthworm used as bait" (with second element from root of twitch), sometimes used in medieval times as a medicament:

For the blake Jawndes take angylltwacches, er þei go in to the erth in the mornynge and fry hem. Take ix or x small angyltwacches, and bray hem, and giff the syke to drynke fastynge, with stale ale, but loke þat thei bene grounden so small that þe syke may nat se, ne witt what it is, for lothynge. [Book of Medical Recipes in Medical Society of London Library, c. 1450]

The people who inhabit the highlands of Southern Brazil have a firm belief in the existence of a gigantic earthworm fifty yards or more in length, five in breadth, covered with bones as with a coat-of-mail, and of such strength as to be able to uproot great pine-trees as though they were blades of grass, and to throw up such quantities of clay in making its way underground as to dam up streams and divert them into new courses. This redoubtable monster is known as the "Minhocao." [Popular Science, August 1878]

"pinch, pluck, twist," usually to the nose, c. 1600, probably from Middle English twikken "to draw, tug, pluck" (mid-15c.), from Old English twiccian "to pluck," of obscure origin; perhaps related to twitch. Meaning "to make fine adjustments" is attested from 1966. Related: Tweaked; tweaking.