weir (n.) Look up weir at Dictionary.com
Old English wer "dam, fence, enclosure," especially one for catching fish (related to werian "dam up"), from Proto-Germanic *wer-jon- (cognates: Old Norse ver, Old Frisian and Middle Dutch were, Dutch weer, Old High German wari, German Wehr "defense, protection," Gothic warjan "to defend, protect"), from PIE *wer- (5) "to cover, shut" (cognates: Sanskrit vatah "enclosure," vrnoti "covers, wraps, shuts;" Lithuanian užveriu "to shut, to close;" Old Persian *pari-varaka "protective;" Latin (op)erire "to cover," (ap)erire "open, uncover" (with ap- "off, away"); Old Church Slavonic vora "sealed, closed," vreti "shut;" Old Irish feronn "field," properly "enclosed land").