The tag io is being used to mean "input/output" (which matches its tag wiki) and for the language Io, which it seems does not have a tag of its own. Something should be done about this. Either create an io-language tag, or shift the input/output stuff to i-o, input-output (which is currently a synonym), or something similar. I'd favour using io-language more as the I/O meaning is used more often.
And, of course, when done, update the tag wikis to refer to each other to try to avoid people tagging their questions badly.