Namesakes
Irish Kings:
3 kings
King Donnchad Midi 770-797 
King Donnchad Donn 919-944
King Donnchad mac Briain 1024-1063
Scottish Kings and Queens:
2 kings
King Donnchad I the Gracious 1034-1040
King Donnchad II 1094
Shakespearian Characters:
1 character
Duncan (a.k.a. Donnchad) Macbeth