'aswarm' originates from English, formed by the prefix 'a-' (from Old English 'on'/'in') attached to 'swarm,' which comes from Old English 'swearm' meaning 'a swarm, multitude.'

'swarm' changed from Old English 'swearm' to Middle English 'swarm.' The adjective/adverb 'aswarm' arose by prefixing Old English 'a-' to forms of 'swarm' in Middle to Early Modern English and eventually became the modern English 'aswarm.'

Initially it meant 'in the state of a swarm' or 'in a swarm'; over time it evolved into the current sense 'full of or swarming with' and is commonly used predicatively (often with 'with').