I’ve seen this word used in the Harry Potter books from time to time. It seems to be used as a greeting, or at least an announcement of one’s presence.
For example, Tonks will notice Harry and say, “Wotcher, Harry, blah blah blah…”
Agreed. I’m not sure why the term’s age means that it must be the ‘cheer’ version. Either is possible, but ‘what’cha up to’ sounds more natural because ‘cheer’ does not have a ‘cha’ sound.
(In case anyone is unaware, the final consonant of ‘what’ and the initial consonant of ‘you’ usually mix into a ‘ch’ sound in spoken Southern British English. I presume everyone understands that, but just in case, you know!)
The cites suggested so far don’t give any concrete evidence for anything other than it being a fairly old expression. Which doesn’t prove any etymology.
How about a cite that the expression “What are you up to?” was used 300 years ago? Sounds very unlikely to me - that’s would seem to be a modern expression, unlike “What cheer.” I can’t recall seeing “What are you up to,” or anything similar, in Defoe, Dickens, or any other pre-20th century author.
Sorry, but that doesn’t make sense. Just because something sounds old-fashioned to us doesn’t necessarily make it older than something which sounds normal.
I’m not sure how this is relevant at all, since the expression under discussion in the OP is “wotcher,” not “wha’cha.” If anything, it is an argument against a derivation of “wotcher” from an expression beginning with “what you.”