dolphin: [13] The ultimate source of dolphin is Greek delphís ‘dolphin’, which some have linked with Greek delphýs ‘womb’. From it was derived delphīnion, a name given to the plant larkspur on account of the dolphin-like shape of part of its flower, acquired by English via Latin as delphinium [17]. Latin took over Greek delphís as delphīnus, which passed into English along two channels.
The classical form was borrowed as delfyn or delphin, which did not survive the 17th century. But the Vulgar Latin form *dalphīnus progressed to Old French daulphin (ultimate source of English dauphin), which English acquired as dalphyn. Dolphin, first recorded in the 14th century, appears to be an English alteration of the form da(u)lphin. => dauphin, delphinium
