rue (v.) Look up rue at Dictionary.com
"feel regret," Old English hreowan "make sorry, distress, grieve" (class II strong verb; past tense hreaw, past participle hrowen), from Proto-Germanic *khrewan (cognates: Old Frisian riowa, Middle Dutch rouwen, Old Dutch hrewan, German reuen "to sadden, cause repentance"); in part, blended with Old English weak verb hreowian "feel pain or sorrow," and perhaps influenced by Old Norse hryggja "make sad," both from Proto-Germanic *khruwjan, all from PIE root *kreue- (2) "to push, strike" (see anacrusis). Related: Rued; ruing.
rue (n.1) Look up rue at Dictionary.com
perennial evergreen shrub, late 14c., from Old French rue (13c.), earlier rude, from Latin ruta "rue," probably from Greek rhyte, of uncertain etymology, originally a Peloponnesian word. The bitter taste of its leaves led to many punning allusions to rue (n.2.).
rue (n.2) Look up rue at Dictionary.com
"sorrow, repentance," Old English hreow "grief, repentance, sorrow, regret, penitence," common Germanic (Frisian rou, Middle Dutch rou, Dutch rouw, Old High German (h)riuwa, German reue), related to the root of rue (v.).
rue (n.3) Look up rue at Dictionary.com
French for "street," from Vulgar Latin *ruga (source also of Old Italian ruga), properly "a furrow," then in Medieval Latin "a path, street" (see rough (adj.)).