disk (n.) Look up disk at Dictionary.com
American English preferred spelling, 1660s, "round flat surface," from Latin discus "quoit, discus, disk," from Greek diskos, from dikein "throw," from PIE *dik-skos-, from root *deik- "to show, pronounce solemnly; also in derivatives referring to the directing of words or objects" [Watkins]; see diction.

Sense of "phonograph disk" is 1888; computing sense is from 1947. Disk jockey first recorded 1941; dee-jay is from 1955; DJ is 1961; video version veejay is 1982. Disk-drive is from 1952.