'soft-shelled' originates from the combination of 'soft' and 'shelled', where 'soft' meant 'not hard or firm' and 'shelled' referred to having a shell.

'soft-shelled' evolved from the Old English word 'scealu', meaning 'shell', combined with 'soft', which has remained largely unchanged.

Initially, it meant 'having a soft outer covering', and this meaning has largely remained the same in modern usage.