From Wikimania

A ting is an online session in real-time using collab-editor software

Origin of the term ting:
Tings (scandinavian spelling, in English things) have been the council-gatherings of the ancient germanians and vikings. It refers to the fact that they had no written language, just as online-ting has no spoken language (at least 'til the idea of voice-tings came up, using VoIP along with the collab-editor session).

List of wikimania-tings

The idea for tinging was made up on the ting-wiki.