'Through' is PIE *terh- (to cross over) — the same root that gives Latin 'trans' and all 'trans-' words.
Moving in one side and out of the other side of an opening, channel, or location.
From Old English 'þurh' (through), from Proto-Germanic '*þurhw' (through), from PIE *terh₂- (to cross over, to pass through, to overcome). Cognate with German 'durch' (through), Dutch 'door' (through), Gothic 'þairh.' The PIE root also gives Latin 'trāns' (across) — the source of English 'trans-,' 'transport,' 'translate,' and 'travel.' The
English 'through' and Latin 'trāns' (across) are cousins from the same PIE root *terh₂- (to cross over). So every word with 'trans-' — transport, translate, transparent, transgender — is a distant relative of 'through.' Even more surprising: 'nostril' comes from Old English 'nosþyrl' (nose-hole), where 'þyrl' means