There was an Aunt Chatty in one of the Green Gables books. Obituaries online seem to confirm that yes, it was a thing, at least in the 19th century - possibly influenced by
Hatty for
Harriet? So maybe Chat started out as Chatty. I don't like it much, but I don't like any other nns for
Charlotte either (it's only two syllables, doesn't need an nn imo), so it's as tolerable as any of them.
I've seen Chartie - or possibly Charty - in some historical literary context too, but can't think where. Not sure if that's 'charty' or 'sharty'. The latter would really not be usable these days, at least in the UK.
eta: which brings to mind
Totty, another vintage
Charlotte nn that's no longer usable.
This message was edited 12/14/2018, 11:23 PM