Where does “できない” come from?

できない (Japanese) comes from Japanese ない, from Old Japanese ない.

Ancestry of “できない”, step by step

できない traces back through 3 separate lines of ancestry.

via Japanese ない

StepLanguageWordMeaning
1Japaneseないhaving that quality, having that state; very much...
2Old Japaneseない

via Japanese [[できる

StepLanguageWordMeaning
1Japanese[[できる

via Japanese でき]]

StepLanguageWordMeaning
1Japaneseでき]]
Every word from Old Japanese ないEvery word from Japanese ない