There's no compelling reason to keep these separate. odor doesn't even have an excerpt.
I'm not seeing an odor tag. If there was before, the questions with that tag have been retagged and the system will delete an empty tag automatically. The odors tag is already configured as a synonym of smell and has been for many years now. The only additional step we can take is to merge the tags so that very old questions with the odors tag get retagged.