I pondered this question mightily for a few seconds and then realized… I haz no fucking clue. So, off to Google I went. Apparently this is an eternal question that has been boggling the brains of peeps for years.
The Grammarist says they’re interchangeable, except for puter stuffs, though his examples lead me to believe that the cookie object should probably be a disk. His commenters, who all sound smart, both agree and disagree. OK.
Wikipedia has an interesting entry on the origin and evolution of the words, mostly focusing on technology. Plus it says that disc is more popular in the UK. Perhaps I was channeling a Brit, hopefully Hugh Grant.
Grammar Girl only talks about the words in puter and medical usage, not the cookie world. Hmm.
Oxford Dictionary backs up Wiki with respect to English-English vs. American.
Overall? I kinda think I should have spelled it “disk,” since I’m American. RAH RAH!
Thanks Roy ~ this was fun! 🙂
(And yes, I use a tilde instead of a dash in informal writing because I’m cool like that.)