spell check anomaly

Had a mainly text spreadsheet, no formulae or cell notes, ran spellcheck and it came up with a word replacement suggestion. It found the word classifié (french for classified)

I didn't remember using a french word. But when I tried to find the word in the sheet, it was not found.

I tried a few different variations, got the same issue, could not find the word or even a derivation of the word (searched for class, for example) then I eventually erased all the text. Ran spellcheck again. Again it flagged the word as misspelled. There are no words in the spreadsheet though.

So what is going on then? see attachment