*ten-

The core meaning of this root was:

stretch, extend

The main offspring are thing and das Ding – yes, hear me out.
In the days of the Germanic tribes, the t(h)ing was the assembly of elders which decided on matters of the community. The Norwegian parliament for example is still called Storting.

The origin of this idea of assembly was probably the stretch of time that the meeting lasted. Like as if we say “Oh man… I have the TWO HOURS tomorrow”. and your coworker might understand that you’re going to have a zoom call.

And then, in German and English, the word shifted from just the assembly toward the matter of the assembly – the issue. And then it broadened to thing.