Old English þræd "fine cord, especially when twisted" (related to þrawan "to twist"), from Proto-Germanic *thredu- "twisted yarn" (source also of Old Saxon thrad, Old Frisian thred, Middle Dutch draet, Dutch draad, Old High German drat, German Draht, Old Norse þraðr), literally "twisted," from suffixed form of PIE root *tere- (1) "to rub, turn." Meaning "spiral ridge of a screw" is from 1670s. Threads, slang for "clothes" is 1926, American English.
The silk line, as spun by the worm, is about the 5000th part of an inch thick; but a spider's line is perhaps six times finer, or only the 30,000th part of an inch in diameter, insomuch, that a single pound of this attenuated substance might be sufficient to encompass our globe. [John Leslie, "Elements of Natural Philosophy," Edinburgh, 1823]
Nuts and bolts you know as little things that put big things together. Actually, our whole industrial civilization hangs by a thread—a screw thread. [Popular Science, March 1949]
"stout cotton fabric ornamented in the loom with raised stripes or fancy figures," mid-15c., dimesey, from Italian dimiti, plural of dimito, a name for a kind of strong cotton cloth, from Medieval Latin dimitum, from Greek dimitos "of double thread," from di- (from PIE root *dwo- "two") + mitos "warp thread, thread," a word of uncertain etymology.
"place (papers) in consecutive order for future reference," mid-15c., from Old French filer "string documents on a thread or wire for preservation or reference" (15c.), earlier "to spin thread," from fil "thread, string" (12c.), from Latin filum "a thread, string; thread of fate; cord, filament," from PIE *gwhis-lom, suffixed form of root *gwhi- "thread, tendon." The notion is of documents hung up on a line in consecutive order for ease of reference.
File (filacium) is a threed or wyer, whereon writs, or other exhibits in courts, are fastened for the better keeping of them. [Cowel, "The Interpreter," 1607]
Methods have become more sophisticated, but the word has stuck. Meaning "place among the records of a court or office" is from 1510s; of newspaper reporters sending in stories, 1954. Intransitive sense "march in a line (as soldiers do) one after another" is from 1610s. Related: Filed; filing.