According to the MDN wiki, DOMContentLoaded will fire when "page's DOM is ready, [although] the referenced stylesheets, images, and subframes may not be done loading."
What about DOMContentReady? Is it just an alias?
I'm making the claim that the event type "DOMContentReady" does not exist in current implementations (meaning, that no current implementation fires such an event type), and that appearances of such a name are merely lapsus memoriae.
The name "DOMContentLoaded" is not easily remembered, and since the jQuery library uses the method .ready() to bind this event type, I guess, some people just mistakenly used the name "DOMContentReady" to refer to the correct name "DOMContentLoaded".