Old Words and Names in the Shire
From Tolkien Gateway
Old Words and Names in the Shire was a short treatise written by Merry Brandybuck sometime after the War of the Ring. It this work Merry discussed the kinship with the language of the Rohirrim of such "shire-words" as mathom and old elements in place names. This treatise was kept in the library of Bucklebury.[1]