Fowling Piece vs. Shotgun

Not an easy question to answer. Language usage changes fairly steadily and quickly, and certain terms show that in their different forms in colonial times and at the present time. In my small database I've noticed one example....they frequently used two words where we use only one. So, early on they used "shot gun", or some variation of it, not "shotgun". The earliest I've collected was from 1734:

The Pennsylvania Gazette
February 27, 1734
"RUN away from Henry Smith's Plantation above Tulpehocken, the
12th Inst. a Servant Man named Tho. Bently, aged eighteen
years, fresh colour, something freckled, had on a brown
Kersey, blue Coat cloth cap, Indian Shoes and Stockings, a
Garlix Shirt; took with him the following Goods belonging to
his Master; Twelve yards of Strowds, Three Indian Blankets,
Twelve Pounds of Powder, Twenty Bars of Lead, Two dozen clasp
Knives, one Shot Gun , a roan Horse marked I. D. on the near
shoulder or buttock, or both,"

It was commonly used in that way in relation to any gun which used shot:

The Pennsylvania Gazette
March 16, 1774
"THO: PALMER Gun Smith AT his Shop, on the North Side of Market street, between Fourth and Fifth streets, hath for Sale, a Quantity of well made RIFLES, that he will dispose of very low for Cash. He likewise makes all Sorts of SHOT GUNS, such as straight Rifles, Cocking pieces, Fuzees, &c. in the best and neatest Manner, which hath gained the Approbation of some of the best Judges within the three Provinces. He also repairs old Work, in the most careful Manner. All Persons who will please to favour him with their Custom, may depend upon his Punctuality and Dispatch."

From British General George Hanger, in _General George Hanger to all Sportsmen, Farmers, and Gamekeepers_, 1814:
"The wild turkey is shot with a rifle; nay, even birds and squirrels, from the very top of the loftiest trees in the woods. No small-shot gun, during my residence of seven years of war in America, was ever kept in the house of a back-woodsman. You will often see a boy, not above 10 years of age, driving the cattle home, but not without a rifle on his shoulder: they never stir out, on any business, nor on a journey, without their rifle; practice, from their infancy, teaches them all distances."

It was in use that way at least until Civil War times:

VINCENNES SEMI-WEEKLY WESTERN SUN
January 16, 1866
"VARIETY STORES VINCENNES, INDIANA KEEPS CONSTANTLY ON HAND, AT THE lowest prices, a large stock of single and double barreled Shot-Guns, Boys' Shot Guns, Revolvers, single and double Pistols, Daggers, Dirk Knives, Bowie Knives, Pocket Knives, Pen Knives, Rasors, Powder Flasks, Shot Bag , Gun Power, Shot, Water Proof Caps, Bar Lead, Buck Shot, Fishing Poles, Fish Lines, Fish Hooks, Fancy Goods, Notions, Toys. Groceries, Tobacco, Cigars, Pipes, Candies, Nuts, Fruits, Sweet Cider, Cakes, Violins, Banjos, Fifes, Drums, Harmonicas, and a million of other useful articles."

I don't know when the usage we are familiar with came along. This blurb from Gilbert Wilson mentions 1876 and uses the joined words, but the article was written in about 1910.

Anthropology Papers of the American Museum of Natural History
Hidatsa Eagle Trapping, by Gilbert Livingstone Wilson
Wolf-chief, speaking of 1876:
“I laid my double-barrel muzzle-loading shotgun behind me on the raft and took off my knife and belt, wrapping it several times around the gun barrel. I habitually carried my ammunition bag on my right side, but I now laid it with the gun and belt at the back of the raft.”

Spence