There are two tags which seem very similar:
Another similar tag is hash-tables, though it is more specific.
If there is any distinction between hash(es) and hashing, the differences are small in the context of computer science. We usually study hash functions to do hashing, and hashing is impossible without hash functions.
Some stats: there are 145 questions tagged hash, 121 of which not tagged hashing as well, and 55 questions tagged hashing, 31 of which not tagged hash as well. This seems to suggest that they are used differently.
One attempt at a distinction:
If we think the difference is pronounced enough to warrant separate tags we should