Role in Henry V sounds like something anyone could play (3)
I believe the answer is:
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for nym that I've seen before include "Criminal crony of Falstaff", "A servant of Falstaff", "One of Falstaff's followers (TMWOW)", "Pistol's companion (Henry V, MWOW)", "Corporal in Henry V".)