Wa-Lau means "Oh my DAD", same meaning of some people say "Oh My GOD". Because the founder was not a religion guy, so instead of using the GOD, it use his own DAD.
Some might use WA-MA! mean "oh my MOM" for those mummy's boy.
And last but not list, the "eh" is just a finishing touch to enchance the words Walau or Wama!
Wa-ma-eh, Who parked the car at my car park.