siditty etymology? BE for feeling superior(1967)

[Douglas G. Wilson]

My best guess (only a guess) is that "siddity" may be derived from
"conceited"/"conceity" in the sense "proud"/"stuck-up"/"vain". There may or
may not have been a form "conceitedy" or so. The final appearance of the
last part of the word (with "t") might or might not be influenced by
comparable "uppity", "biggity".

[DARE doesn't show this sense of the adjective "conceity", but MW3 and SND
show it.]

[The stress in "siddity" is apparently variable, which isn't much help.]

-- Doug Wilson