To a beginning learner like me, these two pronouns, en and y, are so quintessentially French that they seem to have been part of the language since its very inception, really.
However, I have no knowledge of the history of these typically French linguistic structures; nor do I know when they first entered the language.
So my question is: As Latin, the language from which French evolved, seems to have nothing similar to either en or y, what is then the linguistic source for these pronouns in French, and when were they first introduced into the language? (So a very concise introduction to the history of these words would be greatly appreciated).