The names of seven Dnieper rapids in Constantine’s Porphyrogenitus De Administrando Imperio (‘On the Governance of the Empire’) are given both in ‘Slavonic’, i.e. Old (East?) Slavic, and in ‘Rhosic’, i.e. Old Scandinavian, and in addition Constantine explains the meanings of some of these names in Greek. The present paper focuses on the name for the sixth rapid, Βeρούτςη / Λεάντι, and the aim of the author is to show that ‘Rhosic’ Λεάντι corresponds well to Constantine’s Greek translation of this name as ‘the Boiling of the Water’. The etymology to be proposed in this article has its precursor in Bohdan Strumiński’s interpretation of Λεάντι as the present participle form of a hypothetical verb *hløja (‘to boil’), however, the proposal to be presented here refines on Strumiński’s hypothesis by staying with the attested Old Norse verb hlóa rather than resorting to a hypothetical word. One of the difficulties with the verb hlóa is that it is recorded in the dictionary as a hapax legomenon, i.e., as a lexeme attested only once in a single literary monument, but when this verb is situated in relation to the ‘Rhosic’ rapid’s name under discussion, Old Norse hlóa loses its singularity and acquires a derivative in actual 10th-century hydronymy.