the mother of all (something)
The largest, most extreme, or ultimate example of a particular kind of thing. The word that follows "of" is usually plural. Wow, that is the mother of all sandwiches. It's a foot high!
mother of
The best or greatest of a type, as in That was the mother of all tennis matches. This expression originated during the Gulf War as a translation of Iraqi leader Saddam Hussein's term umm al-ma'arik, for "major battle"; the Arabic "mother of" is a figure of speech for "major" or "best." It was quickly adopted and applied to just about any person, event, or activity. [Slang; late 1980s]