'flask-shaped' originates as a modern English compound of 'flask' and 'shaped'. 'flask' originates from Old French, specifically the word 'flasque' (also seen in Medieval Latin 'flasco'), where it meant 'bottle'; 'shape' originates from Old English, specifically 'sceap'/'sceapan', where it meant 'form' or 'to form'.

'flask' changed from Old French 'flasque' to Middle English 'flaske' and eventually became the modern English word 'flask'. 'shape' developed from Old English 'sceap' (and related forms) into Middle English 'shape' and then the adjective-forming past participle 'shaped'; these elements combined in modern English to form the compound 'flask-shaped'.

Initially, 'flask' meant 'bottle' (a container); over time the word kept that sense. 'flask-shaped' has consistently meant 'having the form of a flask' and its basic meaning remains the same in modern usage.