A "house name" is the name under which the house (ancestral home) is known. Usually, it "happens" in smaller villages.
For example, the family's last name can be Novak, and the house is known as "pri Juriju" (at Jurij's). This Jurij person may have lived at the house over 100 years ago (and not be related to the current family living there at all), but the name had stuck and "today" all the villagers know that the house is known as "pri Juriju", but noone knows who this person actually was.
The easiest way to find out a house name is to ask the people living there currently. Unless the name "died out", in which case maybe an older villager remembers, if you're lucky. And sometimes, if you check the matricular books, the house name was noted along with other data.
I hope this makes sense to you.