fem. proper name, biblical ancestor of David, from Hebrew Ruth, probably a contraction of reuth "companion, friend, fellow woman." The Old Testament book tells her story.
"sorrow for the misery of another; repentance, regret," c. 1200, ruthe, from Old Norse hryggð "ruth, sorrow," from hryggr "sorrowful, grieved" (see rue (v.)) + Proto-Germanic abstract noun suffix *-itho (see -th (2)). Or else formed in English from reuwen "to rue" on the model of true/truth, etc. The Old English word was rue (n.2).