English 'can' originally meant 'I know' — from PIE *ǵneh₃- (to know), the same root as 'know,' 'cognition,' 'diagnosis,' 'noble' (well-known), 'narrate' (to make known), and 'ignorant' (not-knowing), making it one of the largest word families in any language.
A modal auxiliary expressing ability, possibility, or permission.
From Old English 'cunnan' (to know, to know how to, to be able to), from Proto-Germanic *kunnaną (to know), from PIE *ǵneh₃- (to know). This is the same root as Latin 'cognōscere' (to know), Greek 'gignṓskō' (I know), and Sanskrit 'jānāti' (he knows). English 'can' originally meant 'I know' — the shift from knowledge to ability ('I know how