Slang term used by students of Carnegie Mellon University's School of Drama to refer to themselves and each other. The term is usually abandoned after graduation, but many graduates go on to bigger and better things anyway. Most other departments use some contraction of their major ("I'm a MechE," "I'm CS," et cetera) but Drama is one of very few to actually invent a longer term for colloquial use.
The name most likely has been derived from the word "dramatist."