Definition of fill out

The expression "fill out" originated in the mid-1800s as a verb phrase that combined the words "fill" and "out." At the time, "fill" was commonly used as a transitive verb to mean "to make complete or whole by inserting something missing" and "out" was a preposition that indicated a location or direction. The specific meaning of "fill out" that we're familiar with today, referring to completing a form or document, likely emerged as a result of increased paperwork and bureaucracy in the late 19th and early 20th centuries. As more forms and surveys began appearing in schools, government agencies, and businesses, people needed a concise and clear way to describe the process of fully completing each required section. Thus, the phrase "fill out" became widely used in administrative contexts, in part due to its efficiency in communicating the desired outcome. Instead of having to say "complete each section of the form or document by inserting the necessary information and making sure no boxes remain empty," the phrase "fill out" conveyed the same meaning more quickly and succinctly. Today, "fill out" is such a common expression that it's appeared in popular culture from time to time, such as in the title of the hit play "The Odd Couple Fill Out the Form" and the popular board game "Fill-a-Pix."