That's the very
thing I'm after Squatter!
Some great speculations and explorations of the words Tolkien created, in the spirit of the way he created and explored language!
The old sense of the word thing conjours up an air of the North, of older times, and in using it for the character of Thingol I get that feeling about him, as of an ancient king, authoritarian and distant. And as one of the senses of the word thing must include Authority, it's a fitting name to choose for the character.
It's interesting that a thing was very much a gathering as well as a parliament, suggesting a bringing together of people, and that was very much the purpose of Doriath, a place where many Elves were gathered together - including Dark Elves. It's also interesting that Thingol ruled over an older established community of Elves in Beleriand, one which was there before the Noldor came back in their blaze of glory;
thing is the old word for parliament, the new one, brought with the arrival of Latin and French was indeed
parliament! What I am getting at there is that in our own languages thing automatically suggests something older - making a poetic link to the older community of Elves ruled over by Thingol.