1) e4 Nc6 is Nimzowitch Defence.
The 1) d4 Nf6 defences are classed as Indian Systems (King's Indian, Queen's Indian, Bogo Indian, Old Indian, etc.) - https://en.wikipedia.org/wiki/Indian_Defence
But does 1) d4 Nc6 have a name?
I recently played somebody who according to my research almost invariably replied to 1) d4 with Nc6. After 2) ... d5 they often transposed into a Chigorin but he often ended up in strange variations of other openings. I have never faced this and decided I needed to do some preparation so I could have some understanding of what kind of positions I should be aiming for and what kinds of traps to avoid.
I could find very little information about possibilities other than Chigorin's and decided that on the night I would chance my arm with 2) d5 aiming for a kind of queenside Alekhine's. Again I couldn't find anything published about this.
On the night he surprised me by replying with 1) ... Nf6 avoiding my last minute prep but falling into my much more extensive experience and knowledge of playing against this. Still, I'm curious.