'convulsant' originates from modern formation based on Latin, specifically from the Latin past participle 'convulsus' (from 'convellere' or 'convellĕre'), where 'con-' meant 'together' and 'vellere' (or 'vellĕre') meant 'to pull or pluck'. The English word is formed with the agent/adjunctive suffix '-ant'.

'convulsus' in Latin passed into Medieval/Scientific Latin and French as forms like 'convulsant', and from these was adopted into English as 'convulsant' with the meaning related to convulsions.

Initially related to the action of violently pulling or twitching (from literal sense of 'torn/pulled apart'), it came to be used medically for violent involuntary muscular contractions and now specifically denotes something that produces convulsions.