see: can Etymology: Middle English couthe, coude, from Old English cūthe; akin to Old High German konda ~ Date: 13th century — used in auxiliary function in the past , in the past conditional , and as an alternative to can suggesting less force or certainty or as a polite form in the present
COULD
Meaning of COULD in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012