I learned the origin of the name "bread-and-butter pickles" today.
Their origin is obscure, of course, as people have been making these kind of pickles for millennia. But the name "bread-and-butter pickles" is easily attributed to Omar and Cora Fanning, Illinois cucumber farmers who started selling sweet and sour pickles in the 1920s. They trademarked the name "Fanning's Bread and Butter Pickles" in 1923.
The story goes that during the post-World War I agricultural slump, the Fannings survived by using undersized cucumbers and bartering them with their grocer for staples such as bread and butter.
Bread-and-butter pickles are a sweet pickle. They consist of cucumbers marinated in vinegar, sugar, and spices. They can be canned or refrigerated.
There are four major kinds of pickle: Dill, Sour/Half Sour, Sweet (with the subsets bread-and-butter and the even sweeter candied), and Pickled Peppers.
Other kinds of pickled vegetables, nuts, or fruits are "pickled [fill in the blank]", apparently.