c. 1300, from Old French orine, urine (12c.) and directly from Latin urina "urine," from PIE *ur- (source also of Greek ouron "urine"), variant of root *we-r- "water, liquid, milk" (source also of Sanskrit var "water," Avestan var "rain," Lithuanian jūrės "sea," Old English wær, Old Norse ver "sea," Old Norse ur "drizzling rain"), related to *eue-dh-r (see udder).
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<a href="https://www.etymonline.com/word/oliguria">Etymology of oliguria by etymonline</a>
Harper, D. (n.d.). Etymology of oliguria. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/oliguria