mid-13c., tohte "stretched or pulled tight," possibly from tog-, past participle stem of Old English teon "to pull, drag," from Proto-Germanic *theuhanan, from PIE root *deuk- "to lead," which would connect it to tow (v.) and tie. Related: Tautness.
It is the hypothetical source of/evidence for its existence is provided by: Latin dux (genitive ducis) "leader, commander," in Late Latin "governor of a province," ducere "to lead;" Old English togian "to pull, drag," teonteon "to pull, drag;" German Zaum "bridle," ziehen "to draw, pull, drag;" Middle Welsh dygaf "I draw."
"pull with a rope," Old English togian "to drag, pull," from Proto-Germanic *tugojanan (source also of Old English teon "to draw," Old Frisian togia "to pull about," Old Norse toga, Old High German zogon, German ziehen "to draw, pull, drag"), from PIE root *deuk- "to lead" (source also of Latin ducere "to lead"). Related: Towed; towing.