"Messrs Achburn, Soulpetre and Ashreborn" and the ingredients of gunpowder in James Joyce's "Finnegans Wake"

In James Joyce's "Finnegans Wake" (1939), a minor figure is introduced with his occupation, nickname, and employer: "A dustman nocknamed Seven-churches in the employ of Messrs Achburn, Soulpetre and Ashreborn, prairmakers, Glintalook [...]" (59.16-18). In "Annotations to Finnegans Wake" (2016), Roland McHugh points out that "charcoal + saltpetre + sulfur = gunpowder", but our reading group was confused at first this evening: "Soulpetre" is saltpetre, but how do "Achburn" and "Ashreborn" correspond to charcoal and sulfur, respectively? Only later did I notice that McHugh's list of ingredients was in a different order than Joyce's names: I'm not sure why "Achburn" corresponds to sulfur, but "Ashreborn" is a good characterization of charcoal. (Andrew Shields, #111words, 1 February 2023)