what does thread mean in that context?
The kind of thread you sew with is what is meant here. I'm not sure if it can be extended to a thread like the one we are all chatting in, as well, or not.
Does anybody know the etymo of the word fadeno?
fadeno = Yid. fodem, Ger. Faden
Source (downloadable)/Fonto (elŝutebla): Esperanto Etymological Dictionary
Don't we all?