Meaning

adjective having finished or arrived at completion

adjective (of a route or journey etc.) continuing without requiring stops or changes

adverb from beginning to end

originFrom Middle English thrugh, thruch, thruh, metathetic variants of thurgh, thurh, from Old English þurh, from Proto-Germanic *þurhw (“through”), from Proto-Indo-European *tr̥h₂kʷe, suffixed zero-grade from *terh₂- (“to pass through”) + *-kʷe (“and”). Cognates Cognate with North Frisian döör (“through”), Saterland Frisian truch (“through”), West Frisian troch (“through”), Dutch door (“through”),…

Etymology from Wiktionary, CC BY-SA 3.0