What exactly was a "mathom house" to a hobbit.

[Rumil]

I guess it had something of the Old Curiosity Shop without the 'Shop' about it. Museums seem to have grown up from the private collections of the nobility in Europe at least. These collections could just as well comprise peculiar anatomical specemins, misunderstood tribal artefacts, religious relics or plain fakes as they could include pieces of great artistic or financial value. Much of present day technology, especially electricity, originated as entertaining after-dinner curiosities and conversation pieces of the well-to-do.

I wonder if originally the mathom house had served as the Arsenal of the Shire, where all the rarely-required warlike gear was stored between emergencies. One ancient near-Eastern king apparently pulled off this trick by appearing merely to be an eccentric collector of military memorabilia until his country went to war, whereupon he immediately equipped his entire army with high quality armour and weaponry, to the amazement of the opposition.