1) An earthernware vessel with a frog in the bottom, especially a drinking pot in the West Riding.
I find no mention of the word in glossaries but antiques take the tradition back to the mid-nineteenth century at least. It may be much older: 1507 I witt to Elesabeth Gascoigne … a grett massar wyth a frouche in the botdom, York. A spelling of ‘frog’ similar to this is listed in the OED, and as a dialect word in the EDD. Note: 1391 cupam meam de murro cum pede argenti in the fronse in fundo cupć, York. Alternatively there may be a connection with 'frounce' whihc could be the ornamental edge of a cup.