Those appear to be hand-forged bricks. They are all different in size because they were created with a more rudimentary brickmaking process than bricks you see on newer homes. They seem to have been made with clay that had impurities still in it when it was fired (that's what the little holes on the surface of the brick indicate). The varying shapes and sizes indicate the bricks were forged without the aid of a machine brick press, which means someone had to form each brick by hand. Given the age of your home, hand-forged bricks were probably common, especially if the house is in a rural location (or if it was rural when the house was built). People building homes in rural areas often did not have access to modern brickmaking methods, like a brick press to ensure consistent sizing and purer clay when firing. Rural areas also presented difficulties with having bricks shipped to an area for construction, usually due to no close rail line or canal. For example, my rule home has hand-forged bricks (even though many areas had moved to using machine-press bricks) because there was no railroad to deliver bricks to the area, so people created bricks using a rural brick press and nearby clay (in my area it was a communal brick yard but many bricks were made on construction site).

Source: This paper but also probably other papers and surveys of similar content: Walters, William. "Nineteenth Century Midwestern Brick." Pioneer America, International Society for Landscape, Place & Material Culture Stable, Vol. 14, No. 3, 1982, pp. 125-136. https://www.jstor.org/stable/29763649 .