In this paper we: provide a brief account of the 1580 and 1808 eruptions on São Jorge in the Azores, which produced Pyroclastic Density Currents (PDCs); discuss the first recorded use of the term nuées ardentes to describe these PDCs; trace how this term was introduced into the scientific literature and discuss its adoption by Alfred Lacroix (1863-1948) to describe the ‘glowing clouds’ produced by Mt. Pelée (Martinique) in 1902. The 1580 and 1808 eruptions on São Jorge are important because they provide early descriptions of PDCs. Documentary evidence of the eruptions and their impacts suggest that the 1580 PDC was a hotter flow, whereas the 1808 PDCs were cooler and more moist. Contemporary accounts describe the 1580 PDC as a ‘globe of fire’, mixed with ‘caustic smoke’ and moving at speed towards the bottom of the slope. In contrast, the 1808 PDCs comprised humid ash, were not incandescent and it is likely that the flows were cooler than that produced in 1580. Since the eruption of Mt. Pelée in 1902, it has been widely accepted that the term nuées ardentes was introduced by Lacroix (1904), being based on his description of the pyroclastic flows that he witnessed. Lacroix acknowledges that the Portuguese expression, nuvem ardente was first used in contemporary accounts of the São Jorge PDCs. This was first translated as nuée ardente and introduced into the scientific by the French geologist Ferdinand Fouqué (1828-1904), who was also Lacroix's father-in-law. Indeed, Lacroix provides an account of the 1580 and 1808 eruptions of São Jorge in his 1904 work La Montagne Pelée et ses Éruptions. The seminal work of Frank Alvord Perret (1867-1943) on the 1929-32 eruptions of Mt. Pelée and his description of nuées ardentes probably helped reinforce the association between the term and Mt. Pelée.