'scrawny' originates from dialectal English/Scots, specifically the dialect word 'scraw' or 'scrawn', where the root carried the sense 'thin, scrawled or scraped'.

'scrawny' changed from dialectal forms such as 'scrawen'/'scrawn' and appeared in 18th-century English as 'scrawny'; the derived noun 'scrawniness' formed later by adding the noun-forming suffix '-ness'.

Initially, it referred to being 'thin' or 'scraped down' (a rough, dialectal sense); over time it evolved into the standard English sense of 'very thin, often unattractively so' and the related sense 'meager or inadequate'.