My guess used to be that it started as a "Klammer-A" ("a in a bracket") and that at some point the joking extension from A to Affe (monkey or ape, everyday Ger

My guess used to be that it started as a "Klammer-A" ("a in a bracket") and that at some point the joking extension from A to Affe (monkey or ape, everyday German does not make a distinction) went viral, supported by the tail-like shape. Now that I know that the monkey connection even exists in languages without the a -> Affe link I'm not so confident anymore.