'kernel-shaped' is a modern English compound formed from the noun 'kernel' and the adjectival combining form '-shaped' (from 'shape'), meaning 'having the shape of a kernel.'

'kernel' comes from Old English 'cyrnel' (a diminutive of 'corn' meaning 'grain'); 'shape' comes from Old English roots (e.g. 'gesceap'/'sceppan' meaning 'form, create'), and the productive compound pattern X-shaped developed in Modern English to mean 'having the shape of X.'

Individually, 'kernel' originally meant 'little grain' and 'shape' meant 'form'; combined in Modern English they now specifically denote 'having the form or outline of a kernel (seed).'