Thaddeus has a genuinely debated root, with proposals linking it to a word for "heart" or "courage" on one side and to "praise" on the other, with no consensus among scholars. Both readings converge on something admired -- either bravery itself or the recognition that tends to follow it.
Anyone who pretends to gather the powers of the stars is forced to assume their character. - Picatrix (Andalusia, ~1000.AD)