*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."
It forms all or part of: bore (v.1) "to drill through, perforate;" Boris; burin; foramen; Foraminifera; foraminous; interfere; interference; perforate; perforation.
It is the hypothetical source of/evidence for its existence is provided by: Greek pharao "I plow;" Latin ferire "to knock, strike," forare "to bore, pierce;" Lithuanian barti "to scold, accuse, forbid;" Old Church Slavonic barjo "to strike, fight," brati "to fight," Russian borot "to overpower;" Albanian brime "hole;" Old English borian "to bore through, perforate," Old Norse berja "to beat, hit," Old High German berjan "to hit, pound, knead."