To save you the click:

"They're not the chairs of the house but the chairs of the house-place, ie. the home. Roughly, nyumbani is used when "home" is used in English and nyumba for "house" but it's a bit more nuanced than that.

There are quite a few of these compounds with a locative noun when the second part essentially tells where something is.

taa za barabarani = traffic lights (lights of on-the-street) simu ya mkononi = mobile phone (phone of in-the-hand) "