Today is the feast of St. James the Greater, also known as Santiago de Compostela, patron saint of Spain. The Bible describes him as one of the first apostles to follow Jesus, and later as a martyr at the hands of Herod. His connection to Spain is… disputed, but tradition stretching back to the 12th century alleges that James went to Spain to preach the Gospel, and after his death, his body was transported back to Spain, where it was interred at Compostela. (Sources differ on whether some of his fellow disciples or a contingent of angels did the transporting.) There is, provably, a cathedral in Compostela with a shrine to the saint. This serves as the termination of the Way of St. James or the Camino de Santiago, a famous and far-reaching pilgrimage network that stretches across a large part of Europe.
Two of the most famous symbols of St. James are extremely common in heraldry. The first is the escallop, or scallop shell. Why, precisely, this is a symbol of St. James is unclear. It may have to do with his origins as a fisherman, but there are other legends about the saint rescuing a knight covered in scallops. In any case, the connection between Santiago and scallops is so well-established that “scallop” in French is coquille St. Jacques, “St. James’ shell,” and in German, it’s Jakobsmuschein, “James’ mussels.” Eventually, the scallop shell became closely associated with the Camino de Santiago, although a lot of that seems to come from pilgrims bringing home shells as souvenirs. However, it’s a very common symbol in architecture and heraldry in northern Spain and southern France where the paths of the Camino de Santiago start to converge. Supposedly, when the escallop is used as a charge in familial or personal arms, it signifies that the bearer or an ancestor went on pilgrimage to Compostela, but I’m highly skeptical of that claim.
Secondly, of course, is the cross of Santiago, the badge of the Order of Santiago. The precise origin of the shape is not especially clear; it might be a sword combined with a scallop shell, or with multiple fleurs-de-lis for honor and purity, or a cross with a sharpened base that could be stuck into the ground, as the Crusaders allegedly carried. Depending on who you listen to, the sword could also symbolize the military valor of the Order’s knights, or the martyrdom of St. James, since he was beheaded with a sword. (I’d personally advise taking all claims of heraldic symbolism pertaining to some intangible virtue and/or more than a couple centuries old with an extremely large grain of salt.) Anyway, the Order was originally founded to protect pilgrims on the Camino de Santiago, but it soon expanded into fighting the Moors, which is how the cross of Santiago ends up on so many Spanish municipal arms.