Reminds me of a garlic keeper.

It looks like a Tagine pot, a type of Moroccan cookware that’s made from ceramic or clay. You make spiced stews with a tagine pot which keeps food as moist as possible while locking in flavors. Typically you place a bed of onions on the bottom, then add meat, vegetables and spices.

The overall shape resembles the tagine pots, but the bottom is much deeper, and there are holes in the bottom. That didn't appear to be characteristic of the tagine pots in my Google search. Garlic keeper looks like a good bet, though the location of the ventilation holes is unlike any I found online, and it's huge compared to many.

Thank you both for joining in the speculation. I grow garlic every year, so for the meantime, it will have a place of honor in the kitchen, full of my own harvest!

Mary

Tagines don’t have holes in the bottom. Maybe a tortilla warmer?

Looks like a hand-thrown piece, so really it could've been for whatever purpose the artist had in mind, and could've been a one-off. My best guess would be a garlic (or onion?) keeper.