As you can tell from the different designs on this page, some family names are associated with many different crests and coats of arms. In fact, these are not all the designs associated with the name Hardin and its variations, but they are the ones most often used.
There appear to be two main branches of Hardins -- one from France via Holland (thus the spellings Hardouin, Hardewyn, and sometimes Harden or Harding), and the other from the United Kingdom (more often spelled Harding or Hardinge).