The cupertino effect is when a word gets changed by an over-enthusiastic spell checker. The term derives from early spell checkers converting cooperation (with no hyphen) into Cupertino, a city in California (see here).
This process can be quite problematic if you try to incorporate non-English words into a text of English. For example, I have found that if I type the Malay word borang ('form in an application'), it gets automatically converted into boring, and similarly datang ('to come') gets changed to dating.
I was just reading a student report which included the Malay phrase:
berberapa keeping gambar
several     ???     picture
It took me a while to figure out that keeping should really be keping, a measure word in Malay, so the phrase means 'several photographs'.