In Doctor Who, S6E7, we learn that we got the word Doctor for being a healer / wise from the doctor:
RIVER: This was exactly you. All this. All of it. You make them so afraid. When you began, all those years ago, sailing off to see the universe, did you ever think you'd become this? The man who can turn an army around at the mention of his name. Doctor. The word for healer and wise man throughout the universe. We get that word from you, you know. But if you carry on the way you are, what might that word come to mean? To the people of the Gamma Forests, the word Doctor means mighty warrior. How far you've come. And now they've taken a child, the child of your best friends, and they're going to turn her into a weapon just to bring you down. And all this, my love, in fear of you.
So, our interpretation of the word is based on the Doctor as being a healer / wise man. But what was the meaning when he took it as his name?