I think it's much simpler: Diskettes, floppy disks etc were invented in the USA, where the standard spelling is "disk". Compact discs were invented by Philips

I think it's much simpler: Diskettes, floppy disks etc were invented in the USA, where the standard spelling is "disk". Compact discs were invented by Philips, who probably preferred the British spelling "disc", and Sony, who probably didn't care. You can find the spelling "hard disc" in RISC OS, a 1990s British operating system: https://www.riscos.info/index.php/Introduction_to_RISC_OS#Using_RISC_OS https://www.riscos.info/index.php/Introduction_to_RISC_OS#Us...