Why is a billboard called billboard?

The name "billboard" comes from a combination of the words "bill" and "board". In the early days, billboards were primarily used for posting public announcements, legal notices, and political messages. These notices were referred to as "bills", and the boards on which they were displayed came to be known as "billboards". Over time, the term "billboard" became the common name for these large advertising structures, which are now used for a variety of commercial purposes.