Hmmm - this is interesting. This means that, if you are right, mav (and I have no reason to believe otherwise) "spoil", strictly speaking, means to make something unuseable or unattractive by taking things away from it.
Which is far from the frequent, modern usage, where you can spoil your picture by ADDING too much paint, or spoil your shirt-front by adding indelible ink (or curry paste - much the same thing in far too many English restaurants!)