you see the word "whatsoever" fairly often, and "whosoever" in some formal contexts (and "whomsoever" in even more formal ones), but why not "wheresoever" or "whensoever" or "whysoever"?
@Felthry (Disclaimer: I have nothing to back the following claim up) I betcha at one point those also existed in English but the use-cases were so rare that they died out. "Where-compounds" used to exist for way more prepositions but they're not used a lot so we basically only kept "wherein." I bet it would be the same for x-soever.
@witchfynder_finder Well, "wherever" is still in common use. As is "whoever", despite the existence of the synonym "whosoever" (which is basically just a more formal term for the same thing)
@Felthry Yeah, they probably got reduced because they're easier to say and the "so" isn't REALLY doing anything except sounding cool.
But I have also done literally 0 reading on this one so don't take this as fact =P
@witchfynder_finder Yeah, reducing words to simpler forms is a common thing! I'm pretty sure it's how we ended up with all the ridiculous pronunciations for UK place-names.
@Felthry That and the fact that any given place has probably had like 3 different names depending on who was invading the countryside that week. =P