When Kevin Creager started his career as a school psychologist in Ohio, little did he know the way parents answered the questions on the developmental history forms could tell him more about his students than the actual answers to the questions themselves.

For instance, when asked "What language is spoken in the home?" one family answered, "We cuss a little." Creager realized answers such as this held the key to understanding his students' home lives-so he spent the next thirty years recognizing and collecting these gems.

In "We Cuss a Little, " Creager compiles over thirty years'...