The Tick seems to have no memory of his life before being The Tick, and indeed not much memory of anything, more than likely due to frequent head injuries.
In the original comic series The Tick is legally insane, having escaped from a mental institution located not too far from The City. In the 1994 animated series he has passed his official superhero initiation test and was assigned to The City. In the 2001 live-action series The Tick was tricked into moving to (and protecting) The City after irritating the employees of a remote bus station he had sworn to protect. He has no memory of his life before that, although Batmanuel suggests that The Tick may be from space. In the 2016 live-action series The Tick has no memory of where he comes from, and his past has not yet been explained or uncovered.