calefactory

noun

cal·​e·​fac·​to·​ry ˌka-lə-ˈfak-t(ə-)rē 

plural calefactories

: a monastery room warmed and used as a sitting room

Word History

Etymology

Medieval Latin calefactorium, from Latin calefacere to warm — more at chafe

First Known Use

circa 1681, in the meaning defined above