'spade-shaped' is a Modern English compound formed from 'spade' + 'shape(d)'; 'spade' (the noun) is used to indicate the familiar tool or card-suit outline, and 'shaped' is the past-participle adjective of 'shape'.

'spade' originates from Old English 'spadu'/'spæd' (from Proto-Germanic *spadō), appearing in Middle English as 'spade'; 'shape' comes from Old English 'gesceap'/'sceap' (Proto-Germanic *skapiz) meaning 'form' — these combined in Modern English to make the descriptive compound 'spade-shaped'.

Initially 'spade' referred primarily to the digging tool (and separately the card suit, borrowed via Romance languages); over time the word was extended to describe anything having a similar outline, so 'spade-shaped' now denotes that outline rather than only the object itself.