plural of rock (n.1). Meaning "ice cubes" is from 1946; slang meaning "testicles" is attested by 1948 in the phrase get (one's) rocks off "achieve intense satisfaction." On the rocks "likely to be ruined or wrecked" is from 1889, a figurative use of the expression with reference to ships (by 1735), with further figurative extension to marriages, romances, etc., by 1958. Of an alcoholic drink, on the rocks, "served over ice cubes," is by 1946.
updated on September 08, 2021