rue

https://www.etymonline.com/word/rue?ref=etymonline_crossreference#etymonline_v_16614

rue (v.)

"feel regret," Old English hreowan"make sorry, distress, grieve" (class II strong verb; past tense hreaw, past participle hrowen), from Proto-Germanic *khrewan(source also of 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.2)

"sorrow, repentance," Old English hreow "grief, repentance, sorrow, regret, penitence," from Proto-Germanic *hrewwo "pain; sadness, regret, repentance" (source also of Frisian rou, Middle Dutch rou, Dutch rouw, Old High German (h)riuwa, German reue), related to the root of rue (v.).