The genus name is a combination of two Greek words radinosus, meaning ‘slender’ and siphon meaning ‘tube’, defining the slender flower tube typical of the Radinosiphon species. The species name leptostachya is also derived from two Greek words, leptos meaning ‘slender’ and stachys meaning ‘an ear of grain or corn’, referring to the shape of the inflorescence. Radinosiphon leptostachya was previously named Lapeirousia leptostachya. Its Afrikaans common name blou angelier translates to ‘blue carnation’ due to the plant’s appearance, even though carnation is a common name normally used for Dianthus species.

Radinosiphon is a genus of flowering plants in the Iridaceae family that was first described as a genus in 1932. It falls under the Crocoideae, one of the major subfamilies of the iris family, containing about 995 species, just more than half of the total species within the Iridaceae. Most of the species in this subfamily are distributed in Africa. The most common species of the Crocoidea are Crocosmia, Gladiolus and Freesia. Typically, the members of this subfamily have sword-shaped leaves, mostly corms as rootstocks, and usually odourless flowers.

Radinosiphon has two species, in South Africa, they have only been spotted in Mpumalanga Province. The other species is Radinosiphon lomatensis and is believed to be endemic to Ehlanzeni district of Mpumalanga Province. Both these species grow from a corm, have sword-shaped basal leaves and 6 petals which are typical features of the Iridaceae family. Radinosiphon lomatensis is easily distinguished from R. leptostachya, by its bigger flowers and longer perianth tube, and its fruit capsules having more than 2 seeds, producing up to 8 seeds per capsule.