The word mathom is in fact a projection by Tolkien of how the Old English word māðm might have evolved if it had survived into modern English. That old word had a similar meaning to mathom as used by the Hobbits, but not quite identical, referring a small treasure or gift such as a ring or a jewel. As a derivation of Old English, the word mathom was not actually used by in the Shire (which long predated that language); instead, it represents a 'translation' of the actual old word used by the Hobbits, which was kastu.

We have no canonical map of Michel Delving, and certainly not of the Mathom-house within it. Much of the map shown here is conjectural, based on the directions of known roads and the larger-scale geography of the region, but it does give some impression of where the Mathom-house lay relative to the better-known parts of the Shire.