[1935–40; sock2 + -o]This word is first recorded in the period 1935–40. Other words that entered Englishat around the same time include: Arts and Crafts Movement, Rhodesian ridgeback, bingo, gangbuster, walk-through-o is a suffix occurring as the final element in informal shortenings of nouns (ammo; combo; condo; limo; promo); -o also forms nouns, usually derogatory, for persons or things exemplifying or associatedwith that specified by the base noun or adjective (cheapo; pinko; sicko; weirdo; wino)