A nick name for the surgeon’s servant on board a man of war, sometimes for the surgeon himself: from the water gruel prescribed to the sick, which is called loblolley.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Lobkin * Lobonian SocietyNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes