"ceremony of burying a dead person," 1510s, probably short for funeral service, etc., from funeral (adj.).
late 14c., "pertaining to the burial of the dead," mid-15c., from Medieval Latin funeralia "funeral rites," originally neuter plural of Late Latin funeralis "having to do with a funeral," from Latin funus (genitive funeris) "funeral, funeral procession, burial rites; death, corpse," a word of uncertain origin, perhaps ultimately from PIE root *dheu- (3) "to die." Singular and plural used interchangeably in English until c. 1700. In Elizabethan times also a verb, "to mourn" (transitive). The classical Latin adjective was funebris.