[thret]

http://chronicle.nytlabs.com/?keyword=disk.disc

[flomo]

What this shows is the old NY Times house style oddity where they described CDs as "compact disks" rather than using the trademark Compact Disc. (Pre-1980, it is not clear to me.)

[CamperBob2]

True. The NYT editorial standards have always been downright bullheaded, even with trademarks ("I.B.M.") where they have no authority to contradict anyone else's usage.

[gpmcadam]

I'm not sure this is a valid comparison as 'disk' and 'disc' aren't synonymous, as evidenced by the lack of a clear pattern of change in the graph.