Pronounced variously:
nick-uh-muh-SHE-an
or
nick-uh-muh-KEE-an
The word Nicomachean is encountered by most people for the first time in an academic setting, in the context of the title of Aristotle's famous treatise on ethical theory, called Nicomachean Ethics. To many students, though, it is unclear just what the word Nicomachean means, let alone what the book's philosophically dense contents are about.
The good news is, at least one part of Nicomachean Ethics has a simple, straightforward explanation. The title is merely a reference to Aristotle's son, Nicomachus, who is believed to have been either the book's editor, or its dedicatee.
Source:
http://www.sparknotes.com/philosophy/ethics/context.html