M8 harsher words like Kurba, etc. are normal and historical Slovene words. The mentioned word is already present in Hieronymus Megiser's dictionary from 16th century. ;) :D Actually i think we are only ones who have word Kurba! I noticed others have Kurva. But yeah anyways harsh words like Kurba were quite despised by the people so in modern times folks think they weren't used but truth to be told when i listen to my grandma's who are both from extreme rurals and have very archaic speech i must say they use really bad words like kurba, pičko, etc. quite alot. However these swears are often (but not always) accompanied with strange add words for example; Pičko goes  Pičko-mar the imitation of piči komar then stuff like jebela cesta or kurberaj, etc. :D

Pardon me, sir, it's my mistake! :( Ofc. kurba is Slovene as all other Slavs use kurva or kurwa (Polish). There is no doubt it was used since "ancient" times and yes, I know rural folks used to swear a lot and awful, in fact they still do today. But afterall, who doesn't?  :D I like those more dialectal: porkamazirja, grumska strela, poršan fizik, jebečko Bosna, mat' petrovška, saprabolt nahamol, tajfl itd.