J.R. Hamilton quotes

That the Macedonians were of Greek stock seems certain. The claim made by the Argead dynasty to be of Argive descent may be no more than a generally accepted myth, but Macedonian proper names, such as Ptolemaios or Philippos, are good Greek names, and the names of the Macedonian months, although differed from those of Athens or Sparta, were also Greek. The language spoken by the Macedonians, which Greeks of the classical period found unintelligible, appears to have been a primitive north-west Greek dialect, much influenced by the languages of the neighboring barbarians. (J.R. Hamilton)