By itself or short for Clifford or Clifton or Heathcliff, this name brings to mind a topographical feature – i.e., what it’ll feel like your kid’s hanging off of every time he climbs more than two feet off the ground.
If you don't call him Cliff Hanger, why even bother naming him Cliff?
Famous people named Cliff:
Actors Cliff DeYoung, Cliff Arquette, and Cliff Robertson III; football player Cliff Harris; baseball player Cliff Lee; bass guitarist Cliff Burton.
Someday your Cliff might make use of CliffsNotes, study guides that are condensed versions of literary works often assigned in school.