Information on a surname prefix / affix + side question

Hello. I am looking for information regarding the surname "Kasprowicz". From what I've gathered "owicz" refers to "the son of". However I can't find any information on the affix "Kaspr" and it doesn't seem like a typical spelling of "Kasper" or "Kacper". Does "Kaspr" mean anything in Polish? Or does it translate to something else longer on its own? I am wondering if the reference to our original surname isn't spelled correctly in this regard. I have done a lot of looking and don't really come up with much.

On a side note, my name is Nicholas and I've found the typical Polish spelling is Mikolaj. Is there a correct short form (nickname)? Like Nick, for example. Miko seemed like the obvious but it doesn't appear common.

Thank you for any insights in advance!

"Kasp" or "Kas" doesn't mean anything in Polish ("Kasa" means "cash money" in colloquial Polish). A short form of Mikolaj? Well, could be Mik, Miko, or Misiu ;) - there's no established short form here.

Any money I would say.

Nicholas, nickname 'Saint/Święty'.