'asprawl' originates from the prefix 'a-' (an English locative or verbalizing prefix) combined with 'sprawl', ultimately from Middle English 'sprawlen' or similar dialectal forms.

'asprawl' developed as a back-formation/compound from the adjective/verb 'sprawl' (Middle English 'sprawlen'), with the prefix 'a-' (from Old English on/at-type use) attached to indicate a state or action, producing the form 'a-' + 'sprawl' = 'asprawl'.

Initially formed simply to mean 'in a sprawled state' (i.e., 'at sprawl'), but over time it came to function as an adjective/adverb and occasionally a verb; the core sense of lying spread out has been retained though the word is now rare/archaic.