Lady's fingers is an alternative English name for okra, the mucilaginous seed pods of a plant of the hollyhock family. Quaintly ancient as it sounds, the term, or at least its application, appears to go back no further than the early twentieth century. First mention of it comes from the USA, restricted in sense to a particular small variety of the vegetable, but it has since broadened out in meaning to cover okra generally. Another plant, however, has a far more ancient claim to the name: the kidney vetch (Anthyllis vulneraria), whose closely bunched head of small thin flowers might be held to resemble a dainty hand (it has been claimed that the ‘lady’ is specifically Our Lady, that is, the Virgin Mary, but there is no conclusive evidence for this). It had the name in the seventeenth century, probably earlier, and held the field apparently unopposed until the later nineteenth century, when a positive cornucopia of fruit and vegetables suddenly started being called lady's fingers, including in the USA types of potato and apple, and in Australia the banana and a variety of grape. Okra seems to have been only one among the bunch, but it has stayed the course better than the others.
One other type of food has shared the name: a sort of small finger-shaped sponge cake: ‘“Fetch me that Ottoman, and prithee keep your voice low,” said the Emperor; “and steep some lady's-fingers nice in Candy wine”’ (Keats, The Cap and Bells, 1820). But here must be mentioned the orthographic uncertainty that has beset the word: a confusing medley of lady's fingers, ladies' fingers, lady-fingers, and others has been used over the centuries. It seems now as established as anything can be that okra is lady's fingers and that, at least in American English, the sponge cake is a lady-finger.