'in-shell' originates from English, specifically the compound of 'in' and 'shell', where 'in' meant 'inside' and 'shell' meant 'a hard outer covering'.

'in-shell' was formed in Modern English by compounding 'in' (Old English 'in') with 'shell' (Old English 'scell' / Middle English 'schel'), producing the descriptive compound 'in-shell' for items kept within their shells.

Initially, it literally meant 'in the shell (inside the hard outer covering)', and this literal sense has persisted into current usage.