ham it up: show off; dramatize yourself

This expression comes from the term ham-fatter, a piece of slang that began appearing around the 1870s. According to musical folklore, old-time jazz musicians always carried a chunk of ham fat for greasing their instruments -- for example, the slides of their trombones. The word might have gained currency through a popular minstrel song titled "The Hamfat Man."

Eventually ham-fatter -- ham for short -- became synonymous with a third-rate musician, then a third-rate performer generally. By the end of the nineteenth century, the term was being applied to vaudvillians, considered much lower down on the talent scale than legitimate stage actors. By the twentieth century, hamming it up meant overdramatizing yourself or showing off. Anyone can do it -- not just actors.

Read more about this expression in Let's Talk Turkey: The Stories Behind America's Favorite Expressions (Prometheus, June 2008).