www.alphadictionary.com

A hot water bath typically used for cooking custards or melting chocolate. It limits and stabilizes the cooking temperature in the dishes placed in it.
Obviously a French term, yet it often appears in English cookbooks when "water bath" is just too dowdy.
Often hyphenated. It has an interesting history involving alchemists, possibly dating back to ancient times.

Mary's Bath. The debate seems to be whether it's Mary of Jesus fame, or a certain Mary the Jewess, mother of alchemy.

Led me to another bathing word; balneal.