axon vs nerve cell

axon

noun
  • A nerve fibre which is a long slender projection of a nerve cell, and which conducts nerve impulses away from the body of the cell to a synapse. 

nerve cell

noun
  • A cell of the nervous system which conducts nerve impulses; a neuron. 

How often have the words axon and nerve cell occurred in a corpus of books? (source: Google Ngram Viewer )