Frigates
sailing warships that often served as scouts or escorts.
Hempen
made from hemp fiber, which is the fiber of the cannabis plant. In the context of the poem, the speaker is probably describing the rigging or ropes on the ship, which were often made from hemp.
Boddice
a garment that covers the torso, typically worn by women and girls.
Aground
(of a ship) touching the ground under shallow water
Opon
Upon
