ivar said:
If you go to a restaurant and ask for "Vieriras" you will get served the shell
better if you ask for 'vieiras'
Scallop in English
ivar said:
If you have to have one during your walk? I have a feeling that these kinds of things are bought at arrival in Santiago, and that many do not actually carry them along the way. I might be wrong.
traditionally, yes. The Liber Sancti Jacobi mentions shells being on sale in Santiago: you wore it on the way back to show that you had been to Santiago and were a returning pilgrim of St James. This was the equivalent of the palm of Jerusalem (a pilgrim to Jerusalem was called a 'palmer' and the reasonably common English surname Palmer comes from that; the less common Romer is from pilgrim to Rome).
In the modern camino cult, though, hardly anyone walks back, and the custom has grown up of wearing one on your way there. This is a modern invention.
ivar said:
Regarding the meaning of the shell, I am not sure. Anyone?
why the scallop became the symbol of the pilgrimage to Santiago is a mystery. Generally explained by the legend of a horseman emerging from the sea covered in scallops, though this is a late legend and probably spurious. In any case, Santiago is not on the sea and, zoologically speaking, St James Scallop, pecten jacobaea, is a Mediterranean species that doesn't occur on the Galician coast. In classical times, the scallop was associated with Venus, though why this should have been transferred to St James isn't at all clear. My own view is that the shell was associated with a fertility cult in Galicia which the Church appropriated, but that's pure speculation on my part. It's further confused by other pilgrim shrines, such as Mont-St-Michel, also adopting the scallop.
For more info on this subject, the oil company Shell published a book on their logo, 'The Scallop', in 1957 for their 60th anniversary, with scholarly articles on the use of the shell, including by pilgrims to Santiago. Copies of this are frequently found in 2nd-hand bookshops; try internet sites of these or places like eBay.
[later edit: the word 'vieira', used in Castilian, Galician and Portuguese, actually comes from venera/Venus. As Ivar says, that's what you'll find on menus, though in Spanish the pilgrim's shell is 'concha de peregrino', from Latin conchylia (ultimately from Greek 'konche'), from which French coquille and English cockle (and conch) also come. Interestingly, the placename Conques also comes from this via the Occitan version 'conca', though apparently from the topography not pilgrim's shell.]