FWIW, from the usual source...
The earlier and better spelling is disk, but disc is now the more usual form in British English, except in sense 2g, where disk is commoner as a result of US influence.]
1715–20 Pope Iliad ii. 941 In empty air their sportive jav'lins throw, Or whirl the disk.[earliest]
g. Computing. A rotatable disc used to store data in digitally coded form, e.g. in a magnetic coating or optically. Cf. compact disc s.v. compact ppl. a.1 II.1c, floppy disc s.v. floppy a. 2, hard disc s.v. hard a. 22c, optical disc s.v. optical a. 6.
See the note to the etymology for the spelling of disc in this sense.