I'm ripping a lot of this from Wikipedia, so credit to whoever wrote it there. I'd attach photos but I'm too lazy to read the copyright licenses on the Wikipedia page to figure out if I can share it. Sorry if the format of this is hard to follow, but maybe next time somebody calls you sugar nips you'll have an opportunity to educate them.
"A sugarloaf was the usual form in which refined sugar was produced and sold until the late 19th century, when granulated and cube sugars were introduced. "
"Households bought their white sugar in tall, conical loaves, from which pieces were broken off with special iron sugar-cutters (sugar nips). Shaped something like very large heavy pliers with sharp blades attached to the cutting sides, these cutters had to be strong and tough, because the loaves were large, about 14 inches (36 cm) in diameter at the base, and 3 feet (0.91 m) [15th century]...In those days, sugar was used with great care, and one loaf lasted a long time. The weight would probably have been about 30 pounds (14 kg). Later, the weight of a loaf varied from 5 to 35 pounds (2.3 to 15.9 kg), according to the moulds used by any one refinery. A common size was 14 pounds (6.4 kg), but the finest sugar from Madeira came in small loaves of only 3 to 4 pounds (1.4 to 1.8 kg) in weight...Up till late Victorian times household sugar remained very little changed and sugar loaves were still common and continued so until well into the twentieth century..."
— Elizabeth David, English Bread and Yeast Cookery
Us white folk sure do go through a lot to make things visually appealing. "To improve the whiteness of the sugar, repeated applications of either a solution of white clay or of loaf sugar dissolved in warm water was applied to the broad end of the loaf."
"The lowest standard refined grades were called bastards, though an even lower grade was often produced from the filtration scums, usually by a scum-boiler at his own separate premises." Pretty sweet job, eh?
It seems that the iconic shape of the sugarloaf had such a cultural significance, it was used as a signal. "The sugarloaf was also the sign of a grocer, often found outside his premises or in the window "
Since settlers had a habit of naming land formations after what it reminded them of, there are a few hills and mountains in the US called Sugar Loaf: At least three other hills or bluffs bearing the name "Sugar Loaf" are located in or near the Mississippi River Valley. As a result of the quantity of places named Sugar Loaf I assume, LF (short for Loaf) became a recognized street suffix by the USPS. You can check the out that suffix and many others in the C1 Street Suffix Abbreviations of Publication 28 - Postal Addressing Standards.