February

The standard dictionary definition for February is very like this one from the AHD:

The second month of the year in the Gregorian calendar.

Modern English February is ultimately derived from Latin; the Latin name for the second month, the name used by Romans, is februarius mensis, “purification month,” or, more literally, “month of purification,” the last month of the ancient (pre-450 B.C.E.) Roman calendar. The month was named after the Roman feast of purification, held on the ides of the month, with the new year starting in the following month.

The etymology of February is a little complicated, in that Modern English February is derived from Latin Februarius, which was used as a direct borrowing in Old English, where the Old English equivalent month, Solmōnað, or “mud month,” is glossed with Latin Februarius. The Latin name for the month was used in addition to the Old English name, and gradually, began to be used instead of the Old English name.

After the Norman Conquest in 1066, the Anglo-Norman French names for the month (also derived from Latin Februarius), Feverer, and Feverier (and other spellings) began to be used, eventually becoming Feoverel.

Spelling reforms in the 15th century attempted to modify English spelling in terms of Latin spelling practices; Feoverel became Februarius, and eventually, February. The pronunciation of February, however, is still a little confusing. As the Usage note in the AHD notes:

Usage Note: The preferred pronunciation among usage writers is (fĕbr-ĕr′ē), but in actual usage the pronunciation (fĕby-ĕr′ē) is far more common and so cannot be considered incorrect. The loss of the first r in this pronunciation can be accounted for by the phonological process known as dissimilation, whereby one of two similar or identical sounds in a word is changed or dropped so that a repetition of that sound is avoided. In the case of February, the loss of the first r was also helped along by the influence of January, which has only one r.

The pronunciation is enough of an issue, still, that entire articles have been written about Why do we pronounce February without the “r”?