I had the realization the other day that the brooch Godrick wears is the spitting image of the Tara Brooch, which “would have been commissioned to be worn as a fastener for the cloak of a high ranking cleric or as ceremonial insignia of high office for a High King of Ireland in Irish Early Medieval society” (x).

Since Limgrave and Stormveil seem very inspired by Ireland and Celtic art—more than Leyndell, where Godrick presumably came from—my guess is that Godrick found the brooch in Stormveil as a relic of the Storm Lord and decided to wear it because it’s gold and pretty (which might be supported by the fact he’s wearing it on the wrong shoulder, according to the wikipedia article.) [edit: it might be the correct shoulder for him after all due to the side his “main” arm is on!]