'head-shaped' originates from Old English elements: the noun 'head' (Old English 'heafod'), where 'heafod' meant 'top, head', and the verb/noun 'shape' (from Old English 'sceapan'/'gesceap' and later Old Norse/Old French influences), where the root meant 'to form' or 'to create'. The suffix '-ed' is the past-participle/adjectival form used to indicate 'having a shape of'.

'head-shaped' arose as a transparent compound in Middle to Modern English by joining 'head' and the past-participle/adjectival form of 'shape' (from Old English roots), eventually stabilizing in modern usage as the compound adjective 'head-shaped'.

Initially it literally described something 'having the form or appearance of a head'; over time the basic literal meaning has remained stable and is still used to describe objects or features that resemble a head.