Hi Ogre.
The derivation of the chords come from the organ music, where you have a set of bass pedals. The cm7(9) is only that, if it is played with a C bass pedal with the EGBD.
If you were to play EGBD with the E bass pedal then this becomes Emin7. The music where this is used quite frequently is in ANDREW LLOYD WEBBER compositions such as 'The Phantom of the Opera' and another is 'I know him so well' from Chess.
There are of course the clever ones who have big enough hands to comfortably cope with the five note chord to make the CEGBD. One of those was the Late Brian Rodwell, who could play Jazz Organ with five finger chords with both hands and play the melody on the bass pedals.

Regards
PeteB