What is the X in X-mas?
late 15c., "act of cooling or freezing," from Latin refrigerationem (nominative refrigeratio) "a cooling, mitigation of heat," especially in sickness, noun of action from past participle stem of refrigerare, from re- "again" (see re-) + frigerare "make cool," from frigus (genitive frigoris) "cold" (see frigid). Specifically "freezing provisions as a means of preserving them" from 1881.
refrigeration re·frig·er·a·tion (rĭ-frĭj'ə-rā'shən)
The act or process of cooling a substance.
The act or process of preserving by cooling.
The reducing of a fever.