Sardiña in Gallicia

Hello to all my Sardiñan cousins.My grandfather was called Sardiña Prieto and originally lived in Galicia - although I'm not sure where.He moved to Almeria in Andalucia, aparently it's not a very common surname there.He was often called 'Sardi' for short.

I wonder if anyone had any ideas on the origin of the name?Has it got to do with a family who fished for sardines? Or did they originate from the island of Sardinia? Or does it mean something else?