E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Emblem of St. James of Compostella, adopted, says Erasmus, because the shore of the adjacent sea abounds in them. Pilgrims used them for cup, spoon, and dish; hence the punning crest of the Disington family is a scallop shell. On returning home, the pilgrim placed his scallop shell in his hat to command admiration, and adopted it in his coat-armour. (Danish, schelp, a shell; French, escalope.)
I will give thee a palmers staff of iyory and a scallop-shell of beaten gold.The Old Wives Tale. (1595.)