'rod-shaped' originates from English, specifically the combination of 'rod' (from Old English 'rodd') and 'shape' (from Old English 'gesceap' / 'scēap'), where 'rodd' meant 'pole, stick' and 'shape' meant 'form'.

'rod' changed from Old English 'rodd' meaning 'pole or stick', and 'shape' changed from Old English 'gesceap'/'scēap' meaning 'form'; the compound 'rod-shaped' developed in Modern English to describe objects having the form of a rod.

Initially, the elements meant 'pole or stick' and 'form' respectively; together they evolved into the descriptive adjective meaning 'having the form of a rod'.