alderman vs councilmember

alderman

noun
  • A member of a municipal legislative body in a city or town. 

  • A long pipe for smoking. 

  • A potbelly, paunch. 

councilmember

noun
  • A councilman or councilwoman; member of a council. 

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