'unshelled' originates from English: the prefix 'un-' (from Old English 'un-') meaning 'not', the word 'shell' (from Old English 'scyl(e)') meaning 'shell/husk', and the suffix '-ed' marking past participle/adjective.

'unshelled' was formed in Modern English by combining the negative prefix 'un-' with the past-participle/adjectival form 'shelled' (Middle English 'schelled', from Old English 'scyl(e)'); over time the components fused into the adjective/participle 'unshelled'.

Initially the parts conveyed 'not' + 'shell' (i.e., 'not having had the shell removed' — with the shell on); usage has stayed focused on whether an item has (or has not) had its shell removed, applied to nuts, seafood, etc.