Orc, actually. Which the JPs tend to depict as piglike because they apparently haven't imported new D&D editions since about the early Nineties (also why their Kobolds are usually small dog-men).
If I were to hazard a guess the Japanese just render the loanword with the closest phonetic equivalent, which Google-sensei then reads as "oak" ¯\_(ツ)_/¯
So for people wondering play time you can beat it in a couple of minutes. It's not long its very very short. You don't even need to grind or fight the monsters.
After you return from the forest with the herbs, magician is in your house. After that, he's waiting at the bottom of his basement, on a fancy throne.
Where is his basement? In his home, hidden under a statue. And his home is near the protagonist's home, on the other side of the church.