"fame, renown, glory," 1799, probably originally in university slang, from Greek kydos "glory, fame," especially in battle, "a poetical word, found chiefly in the Iliad and Odyssey" [Century Dictionary], literally "that which is heard of," perhaps from PIE root *keu- "to see, observe, perceive." In form the word is a Greek singular noun, but the final -s often is mistaken as a plural suffix in English, leading to the barbarous back-formation kudo (attested by 1936).