What is the X in X-mas?
1680s, from French fébrifuge, literally "driving fever away," from Latin febris (see fever) + fugare "to put to flight" (see fugitive).
febrifuge feb·ri·fuge (fěb'rə-fyōōj')n. An agent that acts to reduce a fever; an antipyretic. adj. or fe·brif·u·gal (fĭ-brĭf'yə-gəl, -brĭf'ə-) Acting to reduce fever.