To bring back to mind what was held. Its root is to call back to heart — memory was located in the chest before the head.
Old French remembrer, from Late Latin rememorari: re- (again) + memor (mindful), from a Proto-Indo-European root meaning to remember; to remember is to be made mindful again of something once held in mind.
To bring back to mind what was held. The root's mindfulness is not a metaphor for effort — remembering is, by its own name, a returning to a state of mind rather than a lookup of a fact.