Ta

From time to time, I encounter people on IRC saying “ta” in contexts that suggest they mean “thanks”. I had assumed “TA” was an acronym for “Thanks Again” or some such thing (some acronym site suggests “Thanks Awfully”), but I found out today that this is not the case: “ta” is not an acronym, it is a full word (interjection).

do people actually say “ta”?: It is apparently common in Northern England and parts of London, but it is colloquial, dial. etc. It is pronounced like “spa” or “tar” without the “r”.

Theories of etymology include Scandinavian origin (Viking remnant?) “The online The English-to-American Dictionary also suggests the possibility of Scandinavian origin.” Also, someone on Yahoo Answers (um…) says “The Danish word for “thanks” is “tak”. In Scotland and upper England it was common to drop the “k” at the end because of the way words were pronounced during the time of old English and Middle English.” The same on UrbanDictionary.
But:
Dictionary.com:

[Origin: 1765–75; by infantile shortening and alter.]

Online Etymology Dictionary:

1772, “natural infantile sound of gratitude” [Weekley]

Update:
OED:

An infantile form of ‘thank-you’, now also commonly in colloq. adult use.

So I guess that settles it, and the Scandinavian story is just a folk etymology.

Update:
Lynneguist says “The Urban Dictionary is a hive of folk etymology.” thus ending any credibility UrbanDictionary might have had :)