The origin of the Royal Navyâ€™s nickname is obscure; some sources, including the Admiralty Manual of Seamanship, say that it derives from one Andrew Miller, a zealous officer of the Impress Service during the French Revolutionary and Napoleonic Wars, who â€˜recruitedâ€™ so many men to His Majesty's ships that the navy was said to belong to him.
Earlier (19th century) sources variously suggest that Andrew was a slang name for a man o' war, that Andrew Miller was a supplier of provisions to the Royal Navy, with such an apparent monopoly that he was said to own the Navy, or that the Press Service officer was named Andrew Walker. The most reliable list of Royal Navy officers does not mention either an Andrew Miller or an Andrew Walker.
What is certain, however, is that the Royal Navy continues to be known as the Andrew, and that there is no absolutely conclusive answer to the derivation of the nickname.
According to the story I heard, there was once a 1SL who decided that there was too much swearing in the Navy; that this was unprofessional and it should be toned down.
The word "Harry", for some reason, became a replacement for the adjective "*******". Hence "harry threaders" became a polite way to say "******* threaders" and so forth.
Forgive this addendum, but I 've just realised that Andrew Miller is the Labour MP for Ellesmere Port so I'm not sure if any namesake of his should have his name perpetuated in Naval folklore. B----y Hell, the man is not only a socialist, he's a scouser, probably a football hooligan and nicker of hubcaps.