I did the first one of these in January, and now I’m finally getting around to the second month. At this rate, I should etymologize the rest of the months by 2021!
February—the word, not the month—first showed up in the late fourteenth century, although for a century beforehand we used feoveral, from the Old French Feverier. But apparently the French wasn’t good enough for us, so we decided to spell as it is in Latin, which makes sense since the Old French comes from the classical Latin februarius mensis anyway. Now, that februarius mensis actually means “the month of purification”. The word it comes from is februum, which literally means purgation, a word I had not heard before and absolutely adore . But although we didn’t use any version of February before the thirteenth century, we did still have a name for the month: solmonað, pronounced solmonath, which means “mud month” in Old English. Appropriate, isn’t it? PS. That monað is where we get the word month from.
So why did the Romans name the month the way they did? January was named after a god (Janus). February isn’t so certain. There is an old Etruscan god called Februus, and like I said, the word februum means purge, and at that time of year there was a “festival of purification”, i.e. a purge. But it’s not certain if February was named for the god or the festival or what, just that they’re all connected.
Back when I talked about January, I mentioned that the Roman calendar which ours derives from only had ten months, from March to December. February was added around the time Rome was founded before 700 BCE. Originally, February had a mere twenty three days, but then it was made twenty eight in the effort to make a calendar that made a modicum of sense. Of course, it was only three hundred and fifty five days, and added more on a whim, but baby steps. It wasn’t until 46 BCE that Julius Caesar insisted on making a calendar that wasn’t pure stupid.
TL;DR: February was named for mud, then for purification (or purgation). Also, it has twenty eight days because people don’t know how to make calendars.
Tony Jebson’s page on the Origins of Old English