Filler (noun)

1. A substance used to fill a gap or cavity.
2. A thing or person used to fill a gap or make up a deficiency.
3. A word or phrase added to a sentence to add emphasis or make it more complete.

Origin:

From the verb fill, which comes from the old english word fyllan.

Examples:

1. The carpenter used wood filler to repair the hole in the wall.
2. The singer was a last-minute filler for the concert.
3. The conversation was filled with filler words and phrases.
4. The cake recipe called for a cup of chocolate chips as a filler.
5. The filler episode of the TV show was not well received by the fans.