The in-universe explanation is that his surname is Kravinoff and it was anglicized to Kraven when his family was exiled from Russia. The real world explanation is the character was inspired by General Zaroff from The Most Dangerous Game by Richard Connell and he was a super lame Spider-Man villain for 20+ years until Kraven’s Last Hunt in 1987. So it’s best not to put too much thought into the name beyond accepting that it’s intentionally oxymoronic - it wasn’t supposed to be a flattering depiction of big game hunters.