Attaboy

When someone says "attaboy," they are complimenting a guy's work and showing that they are proud of that person. For example, your dad may be watching your son's baseball game and yell, "Attaboy!" when he gets a hit.

Origin of attaboy

Many sources claim that the slang term "attaboy" comes from baseball in the early 20th century (around 1909). Most uses of the term occurred in baseball as a quick version of "that's the boy!" when people encouraged the players. However, through the years, people began using the term in other contexts, such as work and school, to encourage and compliment others on a well-done job.