I don’t think so. French “tiens” is a form of the verb “tenir” (“hold”). German “tja” is pronounced almost exactly the same and is only used as an interjection with a similar meaning but doesn’t have any related forms that I could think of.
Especially the southern German dialects have quite a few words that originated as loan words from French so it’s at least plausible. Could of course just be a coincidence as well. Languages are full of those.
Just a regular Mastodon server with federation disabled might be a good start.