Related: https://japanese.stackexchange.com/questions/609/the-difference-between-%E3%81%8C-and-%E3%82%92-with-the-potential-form-of-a-verb and https://japanese.stackexchange.com/questions/60066/is-there-a-good-etymological-reason-why-the-potential-form-in-japanese-requires
– mamsterDec 17 '18 at 15:23