Puffin are closely related, together composing the subfamily Fraterculini. The scientific name "Fratercula" is derived from Latin and means "little brother", a reference to the black and white plumage, which resembles monastic robes. The English name "puffin" – puffed in the sense of swollen – was originally applied to the fatty, salted meat of young birds of the unrelated Manx shearwater ("Puffinus puffinus"), formerly known as the "Manks puffin". Puffin is an Anglo-Norman word (Middle English "pophyn" or "poffin") for the cured carcasses of nestling Manx shearwaters. The oldest alcid fossil is "Hydrotherikornis" from Oregon dating to the Late Eocene while
Christmas shearwater subalaris"). The Christmas shearwater is a slender-bodied shearwater, about 36 cm long, with a wingspan of around 75 cm, and weighs around 350 g. It has dark plumage all over, generally blackish-grey with a rusty-brown tinge, slightly paler on the underside of the bird, and with some small edging of white under the chin and pale fringes to the upperwing coverts. It has brown-grey feet and a dark bill and eyes. Both sexes are alike, as are the young after fledging. Nestlings are covered in dark grey down feathers. The species closely resembles the sooty ("Puffinus griseus") and short-tailed shearwaters