maisonette (n.)

1818, "small house," from French maisonnette, diminutive of maison "house" (11c.), from Latin mansionem (see mansion). Meaning "a part of a building let separately" is by 1889.

You see, this is how it stands: I live in what the fellow who let the thing to me called a "maisonette"—goodness only knows why .... [Windsor Magazine, 1902]