The Ancient Greek word it comes from is (w)oida, "I know". Structurally, it's the perfect tense of (w)eido, "I see": knowing something is equivalent to having s

The Ancient Greek word it comes from is (w)oida, "I know". Structurally, it's the perfect tense of (w)eido, "I see": knowing something is equivalent to having seen it, for Ancient Greeks. I loved reading that in the dictionary. Their word that properly meant "I have seen" was "(w)idon"; the wid- root comes into English as wit/witty, and via Latin as video and visual.