It is basically a Peel (German/Patrick border)name, probably same derivation as Kerruish and also has Irish cognates which may also explain some Peel links but fount as McCorris from 1511 and there's not many records before that - I have 6 corris families + a widow Corris in Peel 1814 census - the IGI sometimes renders it as the more common Corrin - also look for Corras.
There are 254 pages with name Corris on my site
When you say you have the Patrick/German parish regs I presume you mean the 1911 transcription of these which itself may well contain errors - I have seen the 'real' german reg (and transcribed a fair amount of it) but the Patrick reg has not yet appeared in the Museum though legally it should have.