The masculine name is not Ophrah but "Offer", the addition of the "ah" at the end of a name turns any Hebrew name to a feminine name (Yosef-Yosefa and so on).And BTW, the name of the famous TV host, Oprah Winfrey, was not derived from this name, but was originaly "Orpah" (from the Book of Ruth, a not so loveble character, from the Hebrew word "oref", the back of the head, because she turned her back, while Ruth stayed), but no one could pronounce it, so it came out Oprah.