It's unknown of what his actual name is. TLK:SNA books are not Disney creation but outsider written. Alex Simmons who wrote the first book of the set "A Tale Of Two Brothers" came up with Taka for Scar's name. Simmons never worked with Disney and he had their permission to release the books only in USA. I could assume that Scar was jealous of Mufasa even before Simba was born. that's how he was behaving like he was in the film. as far as his scar goes it maybe that he gotten the scar when he was born when his mother cut him accidentally by stepping on him or he might of clawed himself by accident from birth. since Scar is brown it can be possible that his name is Kahawia which means brown in Swahili. But Scar is just Scar in the film universe it's self no filmmaker has given him an actual name.