語源は不明。おそらく古英語のheag, mate, fearr, bullから。すなわち、雄牛と交尾する牛。
Old English seems to have had the word *h?gfore 'heifer.' The first element (*h?g-) presumably meant 'enclosure' (as do haw and hedge), whereas -fore was a suffix meaning 'dweller, occupant' ....In modern use a female that has not yet calved, as opposed to a cow, which has, and a calf, which is an animal of either sex not more than a year old. As derisive slang for "a woman, girl" it dates from 1835.