Ah, right! So I think "Ta" is a short saying that's comming from ~ "Tank you" ("thank", pronounced without h) There (http://encarta.msn.com/encnet/features/dictionary/DictionaryResults.aspx?refid=561508481)
I'm pronouncing "thank you" as "fank you" (fenk you), however some people says it like "sank you" (or "senk you")...
Well, as the only one here who uses it, and it is used a great deal here in England, let me explain.
Dunno.
Oh, all right then
It is a very old expression. (The evolution of words is such that very short words tend to be very old as they don't change much).
Here's one explanation of the brymological roots of the word.
The word may be a result of the heavy Scandanavian influence on the English language.
The Danish word for "thanks" is "tak". Over time, the "k" got dropped. Probably in the time between 1,000 A.D and 1100 A.D, when the Norman influence was at its zenith, (but who can tell) because of the way we believe that words were pronounced during the period Old English and Middle English were spoken.
In case you aren't aware, it is pronounced so it rhymes with "tar" or "car", but the "r" sound is very slightly shortened compared to the word "tar".
The English language is divided into three periods:
Old English, also called Anglo-Saxon, from the 400s through 1066.
Middle English from 1066 to about the 1400s and
Modern English from the late 1400s onward.
Example (from monastic records, as there is little else that spans the period):
Old EnglishUren Fader †at art in heofnas
Sic gehalyed †in noma
To cymeð þin ric
Middle EnglishOur Fadir that art in heuenes
Halewid be thi name
Thi Kingdom comme to
Early Modern EnglishOur Father who art in heaven,
Hallowed be thy name.
Thy Kingdom come