Definition of pump up

The expression "pump up" originated in the context of pumping up tires on vehicles. It dates back to the late 19th century when air inflated tires began to replace the traditional solid rubber tires. The verb "to pump" initially referred to the act of adding air or compressing fluid in a container using a pump. Essentially, "pump up" is a phrasal verb that has evolved from this meaning and now commonly refers to increasing the volume or intensity of something, such as pumping up one's confidence, pumping up the volume on a stereo, or pumping up an athletes' performance. The phrase has become a popular idiom in casual English, and its usage continues to grow as technology advances and new contexts emerge.