Grog is essentially a diluted rum mixture, with two parts water and one part Pusser's Rum. The word "grog" was derived from the nickname for Admiral Vernon who was nicknamed "Old Grogram" (grog, rum - get it?!) based on the waterproof grogram cloak he wore on ships. He first ordered this rum dilution process that yielded grog to be carried out in 1740. This command was called "Vernon's Orders" and it also encouraged the addition of sugar and limes to the grog mixture - which is the present day Pusser's Rum recipe for grog.

The method of issue and the mixture of the Pusser's Rum changed over the years. Prior to 1740, rum was issued to the men neat or in "drams" - without water. Admiral Vernon (pictured at right), the hero of Portobello and the Commander-in-Chief, West Indies changed all this by his issuance of his infamous Order to Captains No. 349 on August 21, 1740. His order refers to the "unanimous opinion of both Captains and Surgeons that the pernicious custom of the seaman drinking their allowance of rum in drams, and often at once, is attended with many fatal effects to their morals as well as their health ... besides the ill consequences of stupifying [sic] their rational qualities ... You are hereby required and directed ... that the respective daily allowance ... be every day mixed with the proportion of a quart of water to a half pint of rum, to be mixed in a scuttled butt kept for that purpose, and to be done upon the deck, and in the presence of the Lieutenant of the Watch who is to take particular care to see that the men are not defrauded in having their full allowance of rum... and let those that are good husbanders receive extra lime juice and sugar that it be made more palatable to them."