To unlock this achievement you need to click to objects/monsters in the dungeon in this sequence: Barrel, barrel, Zombie, barrel, barrel, barrel, Zombie, crap while:
Zombie is reffered to any monster of the zombie family, those with green poisonous hearts.
Crap means "Slightly used coin", looks like crap and gives you 1 gold.
You can't collect any items/coins or attack other enemies in the sequence if you want to unlock Einy, meeny, miny moe so clear the place a bit before attempting.
The Catacombs are the best place to farm this achievement. Once you find a level with a lot of barrels and a zombie, you can click on them as stated above. Be careful with barrels, they sometimes explode so it's better to choose some that are further from others. "Clicking on zombies" means hitting them to take away at least one heart, you can click on two zombies or hit one , then destroy three barrels and then hit the same zombie again.