[Book] Prof. Eleonora Matarrese * Nymðe - The Unearthing

[Stefan Wirtz_2]

Well,[..]
I'm pretty sure there is a connection since even now Tanacetum is the herb "of the Germans". [..]

Well, I am German and have not the slightest idea how you came to this statement.
If there was any „herb of the Germans“ (regarding those who are not relevant for brewing), it 
would be Kamille, Matricaria chamomilla.

Tanacetum, Zitronenmelisse, is just one of many herbs, and no one would consider it very important or relevant.
Even more, T. has it‘s origin in eastern mediterranian and Caucasus regions, which is more „my direction“ of understanding.
But this does not mean I would even see your identification as right.
And I heavily doubt that your interpretation aka translation has anything to do with a „Germanic“ language, be it medieval or even older.