Imbolc

Learned borrowing from Old Irish Imbolc, originally the name of a pagan festival, later a name for Candlemas. The etymology of the Old Irish word is uncertain; common explanations include the following: * From Old Irish i mbolg (“in the belly”), referring to pregnant ewes. * From Old Irish imb-fholc (“to cleanse or wash oneself”), referring to a ritual cleansing. * Perhaps from Proto-Indo-European *h₂melǵ- (“to milk; milk”), though the connection between the milking of animals and the festival is not clear. Some descendants of this root have meanings related to cleansing (for example, Persian مالیدن (mâlidan, “to rub, smear”), Sanskrit मर्जति (marjati, “to clean, wipe”)), so the root could also have the sense of purification.

来源：wiktionary