My case is:
I had a field called status. Then I renamed it to Status. Then for testing I renamed it to StatusSSS.
Both status and StatusSSS remained in the View Designer, but only in the view that has used it.
Compacting did not immediately help.
What is the background with the field names? Where do they get stored except by using them in documents?
Subject: Deleted field names continue to appear in View designer
Notes stores all used fieldnames in a separate ‘places’ in the nsf-file.The only way to delete unused names is to create a new replica
Subject: RE: Deleted field names continue to appear in View designer
What excactly do you mean by “place”?
Subject: RE: Deleted field names continue to appear in View designer
Fields are stored as design notes as part of the form. Deleting the field leaves the design note so you can still refer to it in the event you stored forms with the documents.
Check the R5 forum for much more in-depth discussion of this topic, it has been covered eleventy billion times and there is no good universal solution.
– Charles
Subject: Sure even Domino can’t store eleventy-billion documents? 
(WAS: Deleted field names…)
Subject: RE: Deleted field names continue to appear in View designer
They are also stored in the Item Definition table, you can view this with NotesPeek.