A full explanation can be found here, but here’s an extract:
Today is a day of purification, renewal, and hope. On this day, exactly 40 days after Christmas, we commemorate Mary’s obedience to the Mosaic law by submitting herself to the Temple for the ritual purification, as commanded in Leviticus.
However, the Obscure Goddess Online Directory (!) notes:
Juno Februtis is an aspect of that great Roman Goddess as a purifier and fertility Goddess, who was especially connected with the month of February and the festivities in its latter half. She would seem to be related to Juno Lucina as a childbirth Goddess. February was the month of purification to the Romans because in their early calendar it was the last month of the year, and so considered an appropriate time to get rid of the bad, stale, or unclean in preparation for the new year.
This was new to me, but it’s an interesting, um, coincidence if accurate.