Summarily in Aristophanes in Plutus [Wealth]: "what doctor, then, is there now in the city?".[1]
But in Homer [sc. more fully]: "a doctor man, you see [...]".[2]
"A doctor [is] an expert, someone who not only heals but also knows the basis for the healing".[3]
But [sc. note also the term] medical-practitioners. [Note] that doctors also wrote about airs, mountains and waters. There are compositions of Hippokrates written on such subjects: about airs, places and waters.[4]
[Note] that doctors are in the habit, through boastfulness, of naming plants after their native countries, such as 'Cyrenean' juice, 'Lakonian' spurge.[5]
And present-day ones [speak of] Pontic Rhubarb and non-Greek Rhubarb.[6]
For doctoring see under health [upsilon 23].