What is "eieio"

EIEIO may be:

• The refrain to the children's song, " Old MacDonald Had a Farm"
• Enforce In-Order Execution of I/O, a machine instruction used on the PowerPC computer processor
• Computer bought the farm, an error message with symbol EIEIO, from the GNU Hurd operating system
• EIEIO, an emacs lisp library that implements the Common Lisp Object System. It is packaged with CEDET (Collection of Emacs Development Environment Tools), which itself is part of GNU Emacs.
• "E-I-E-I-O", an episode of Barney & Friends from the fourth season of the show.