Please let me know: Is there any specific word for removing grain from the cob?
Also, is there a proper word for its outer covering?
The expression you are looking for is to shell cobs:
- to remove peas, nuts, etc. from their shells or their natural covering.
- is a hand-held device or a piece of machinery to shell corn kernels of the cob for feeding to livestock or for other uses.
The outer green cover is called "husk":
- the dry external covering of certain fruits or seeds, especially of an ear of corn.
On the farm I grew up on in PA we called removing the outer husks from the cob husking and removing the hard corn from the cob shucking.