I'm researching the origin of various greetings for an upcoming BBC Radio 4 programme on linguistics. Any input on regional/national specific greetings would be welcome. For instance, is the US 'howdy' just a national variant of 'how do you do?', as it appears to be? If so, when did it begin to be used in the US? Any other US greetings that have parallels/origins in the UK would be useful too.
Why is 'wotcha', which was used in mediaeval England as 'what cheer?', now primarily a southern UK/London expression? Likewise, why is 'tarrar' which, as Victoria has suggested, is probably a version of 'ta-ta', primarily northern?