Talofa
My mother saids that Sauvao was the matai name and was given to Motu, not sure as to Siata's maiden name but will check with family.
My mothers father's name is Faaota'ota and their surname is Pasene. I do not know the history of the matai titles Motu, as for Pasene it does not seem to have been referred to as a matai title at present no one in my mothers family have received a matai.
Thank you Faapaia