Accelerant

wiktionary

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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). [1]

etymonline

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accelerant (n.)

"that which hastens," especially combustion, 1854, from Latin accelerantem (nominative accelerans), present participle of accelerare "to hasten, quicken" (see accelerate). As an adjective from 1890.