mether
A communal drinking vessel used in Gaelic times for drinking mead. It had squared sides and one drank from a corner. Also, a trophy in this shape.
historical
Filled with Mead Made from honey of the heather
I raise to you, O Queen, this Loving Cup, this Mether,
Where it comes from
From Irish meadar, from Old Irish metar, from Latin metrum. Doublet of metre, meter, and metron.
Adapted from the Wiktionary entry mether (CC BY-SA 4.0).