The story
From accelerate + -ant (suffix forming agent nouns from verbs, or forming adjectives with senses of being prone or tending to do the actions of verbs).
Etymology from Wiktionary, CC BY-SA 4.0.
accelerant
ac·cel·er·antToday it means: In the context of fire protection, a substance that accelerates the development of a fire, especially some hydrocarbon-based fuel used to spread a fire caused by arson. Full definition →