This seems like a very strange question, I know. It actually has three parts:
- Does anyone of Thorins company ever call Bilbo a "hobbit"?
- If so, how would they know what a hobbit was unless Gandalf had told them?
- Is Gandalf the only way the dwarves would have known what a hobbit was?
Let me explain further. In Tolkien's Unfinished Tales, we read:
Gollum would not know the term "Hobbit," which was local and not a universal Westron word.
We also read that:
[Gollum] dared to pretend that he believed that the land of the halflings was near to the places where he had once dwelt beside the banks of the Gladden.
After taking a look at map, I see that Erebor and gladden fields are all right next to each other, however, gladden fields are even closer to The Shire than the lonely mountain.
This got me thinking - If Gollum would not have known what a "hobbit" was, how would the dwarves?