History: What does a de-esser do?

What does a de-esser do?

• A de-esser reduces the amplitude over a threshold.
  That is a compresor.
• A de-esser is a collection of individual compressors for specific frequency ranges.
  That is a multi-pressor.
• A de-esser increases the amplitude over a threshold.
  That is an expander.
• A de-esser targets a specific band of frequencies and reduces the amplitude on specific ranges.
  Great job!