Why Royal Navy leaders are called Sea Lords

Why are they called Sea Lords?

Their authority descended from the Lord High Admiral's commissioned office, and the title later distinguished professional naval members from the civilian First Lord and other Admiralty politicians.

The title grew from officers exercising authority derived from the Lord High Admiral when that office was placed in commission. Its feudal language described the authority being exercised before it became a label for a modern naval profession. As the First Lord of the Admiralty became the civilian political head, naval members needed language that marked their professional service identity. Sea Lord therefore distinguished the uniformed naval leadership from civilian Lords of the Admiralty.