My theory ffor the chicken of the sea thing:
Chicken is a very common Bird that lots of people eat. It walks on land.
Tuna is a very common fish that lots of people eat. It swims in the sea.
They are similar which makes them seem like the very common Chicken
but They are in the Sea.
Thus the name chicken of the sea.....
Its common sense!
and I think too much! YAAY!