Smials
From Tolkien Gateway
The term the Hobbits themselves used for the "more luxurious versions of the simple diggings of old" inhabited by the well-to-do. "But suitable sites for these large and ramifying tunnels .... were not everywhere to be found" so many Hobbits lived in wood, brick or stone houses. The poorest, however, "went on living in burrows of the most primitive kind, mere holes indeed, with only one window or none". - Source: The Lord of the Rings, Prologue, 1. Concerning Hobbits.
A more common term for the Hobbits' excavated dwellings is 'hobbit-holes'.
