Old English þrescold, þærscwold, þerxold, etc., "door-sill, point of entering," a word of uncertain origin and probably much altered by folk-etymology.
The first element probably is related to Old English þrescan (see thresh), either in its current sense of "thresh" or with its original sense of "to tread, trample." The second element has been much transformed in all the Germanic languages, suggesting its literal sense was lost even in ancient times. In English it probably has been altered to conform to hold.
Liberman (Oxford University Press blog, Feb. 11, 2015) revives an old theory that the second element is the Proto-Germanic instrumental suffix *-thlo and the original sense of threshold was a threshing area adjacent to the living area of a house. Cognates of the compound include Old Norse þreskjoldr, Swedish tröskel, Old High German driscufli, German dialectal drischaufel. The figurative use was present in Old English.
*terə-, Proto-Indo-European root meaning "to rub, turn," with derivatives referring to twisting, also to boring, drilling, piercing; and to the rubbing of cereal grain to remove the husks, and thus to threshing.
It forms all or part of: atresia; attorn; attorney; attrition; contour; contrite; detour; detriment; diatribe; drill (v.) "bore a hole;" lithotripsy; return; septentrion; thrash; thread; thresh; throw; threshold; trauma; trepan; tribadism; tribology; tribulation; trite; triticale; triturate; trout; trypsin; tryptophan; turn.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit turah "wounded, hurt;" Greek teirein "to rub, rub away;" Latin terere "to rub, thresh, grind, wear away," tornus "turning lathe;" Old Church Slavonic tiro "to rub;" Lithuanian trinu, trinti "to rub," Old Irish tarathar "borer," Welsh taraw "to strike."
1560s, "to thrust out, remove, throw out of doors," from Latin eliminatus, past participle of eliminare "thrust out of doors, expel," from ex limine "off the threshold," from ex "off, out" (see ex-) + limine, ablative of limen "threshold" (see limit (n.)).
Used literally at first; the sense of "exclude, throw aside, or disregard as undesirable or unnecessary" is attested by 1714; the sense of "expel waste from the body" is by c. 1795. Related: Eliminated; eliminating; eliminative; eliminatory.
1580s, "expressing lofty ideas in an elevated manner," from French sublime (15c.), or directly from Latin sublimis "uplifted, high, borne aloft, lofty, exalted, eminent, distinguished," possibly originally "sloping up to the lintel," from sub "up to" (see sub-) + limen "lintel, threshold, sill" (see limit (n.)). The sublime (n.) "the sublime part of anything, that which is stately or imposing" is from 1670s. For Sublime Porte, former title of the Ottoman government, see Porte.