I searched also for a dublicate of this question but I found nothing.
marked as duplicate by Charles, Bo Persson, Rory, yhw42, animuson Dec 8 '12 at 17:51
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
The correct term is burnination:
Put in a request here on meta when you see tags that need merging/burnination, and the mods will do it for you.
If you see tags that are only on a few questions, untag them; the system will automatically delete tags after a period of inactivity. You can, once again, ask for help here on meta with untagging.