Lesson Six   Motivation
Onomatopoeic motivation     
Primary onomatopoeia
It means the imitation of sound by sound, the
  imitation of sound by human speech sound. Here the
  sound is truly an “echo to the sense”.

Secondary onomatopoeia
Secondary onomatopoeia means that certain
    sounds and sound sequences are associated with
    certain senses in an expressive relationship. It
    refers to sound symbolism.