- ruthenium (n.)
- metallic element, 1845, named by Russian chemist Karl Klauss, from a name proposed earlier (1828) in reference to a metal extracted from ores from the Ural Mountains of Russia (see Ruthenian).
- ruthless (adj.)
- early 14c., with -less + reuthe "pity, compassion" (late 12c.), formed from reuwen "to rue" (see rue (v.)) on the model of true/truth, etc. Ruthful (early 13c.) has fallen from use since late 17c. except as a deliberate archaism. Related: Ruthlessly; ruthlessness.
- Ruy Lopez
- type of chess opening, 1876, from Ruy López de Segura (fl. 1560), Spanish bishop and writer on chess, who developed it.
- Rwanda
- African nation, named for indigenous people there, of unknown origin.
- rye (n.)
- Old English ryge, from Proto-Germanic *ruig (cf. Old Saxon roggo, Old Norse rugr, Old Frisian rogga, Middle Dutch rogghe, Old High German rocko, German Roggen), probably originally from Balto-Slavic (cf. Old Church Slavonic ruzi, Russian rozhi "rye;" Lithuanian rugys "grain of rye," plural rugiai). Meaning "whiskey" first attested 1835.