A small story behind the reason for this question.
In Russian, just as in English, many fundamental words are a combination of two basic ones. The verb "forgot" is "zabil" in Russian. It is formed by "za" - in this case most likely in the meaning of "after" - and "bil" - literally "was" or "I am in the past". If you put them together, it forms a logical structure of "after the way I was".
In English we have "forget/forgot". As it happens in Russian, it is formed by "for" and "get" in different tenses. What meaning do these two words logically take (if any), to be righteously forming the word that logically means "to lose something that was known"?