What is the origin of the idiom "smack dab" and when to use it?

The origin of the idiom "smack dab" is somewhat uncertain, but it is believed to be of American origin. It likely emerged in the United States, particularly in the American Midwest, in the 20th century. The phrase combines the words "smack" and "dab" to emphasize the precision and centrality of the location or placement of something. "Smack" in this context means "directly" or "squarely," and "dab" refers to a small, precise amount or touch. When used together, this expression is used to describe something that is positioned or located directly in the middle or at a precise point, often with an emphasis on the unexpected or noticeable placement.