februum.

Perhaps from Proto-Italic *feɣʷrwom (“belonging to an offering, means of purification”), from Proto-Indo-European *dʰégʷʰrwom, from Proto-Indo-European *dʰógʷʰrus (“belonging to a burning, an offering”), from *dʰegʷʰ- (“to burn, warm”), doublet of febris. Varro mentions that the alternative form "februm" derives from the Sabines. This etymology is likely false; the term likely has Latino-Faliscan origins due to the morpheme *-br-, whereas in Sabellic it would have been *-fr-. Throughout Roman literature, the term is associated with the distant past; authors routinely mention that it was used by the "ancients." It is likely that Varro was compelled to provide Sabine origins for the term due to their connection with Rome's mythological past. Instead, the term may simply have been an archaic Latin word. It was often used within a religious context and religious terminology can be archaizing.