Hello
i can't understand the links between
Sap-Uidia > Sapaudia > Savoie France = "Wood Firtree"
Sap- = Fir from may be IE Seib = to drain/drip ? because of fir resin ?
and
IE Sap- > Dyeing/Soap
see here
http://www.etymonline.com/index.php?search=soap&searchmode=none
and Celtic Sapana- = Pimpernel
Pseudo-Dioscoride (2.178) : "Anagallis phoeniceaÂ…Galloi sapana"
Plant with a lot of saponine