From the movie Goodfellas:
A woman shows her two friends her new home.
Woman: Four and a half months of dirt.
One of her friends: It's so good.
Woman: I did it. Do you love it?
Her friend: Oh it's beautiful.
It seems "dirt" possibly means "hard work", but it doesn't have such a definition in dictionaries. The closest definition is "filth". Is "dirt" here a slang usage?