a teaching/research 'fellow' [=a graduate student who gets money in exchange for teaching/research]
He attended the concert with a 'fellow' student. [=someone who is a student, as he is]
He has always tried to be of service to 'his fellow man'. [=to other people]
(..) There's still nobody in the world... ...who can play "As Time Goes By" like Sam. He hasn't played it in a long time. Good night. Good night. A very puzzling fellow. What sort is he? I really can't say, though I saw him quite often in Paris. - Tomorrow at at the prefect office. - We'll be there. (..)1942 Casablanca
(..) Watch yourself. Be on guard. This place is full of vultures. Vultures everywhere. Everywhere. - Thank you. Thank you very much. - Not at all. Amusing little fellow. Waiter. - How silly of me. - What, dear? I've left my wallet in the hotel. Perhaps tomorrow (..)1942 Casablanca