On other hand, this could be germanic version of Ratnieki.
Ratnieki town or burg are in Liepaajas, Madonas and Reezeknes districts.
There probably are others...........
Archbishop Albert in 1254 wrote about Upmala (as Zemgale center) “terrarium Opiten et Saulen” - “Upite and Saule”.
but the comment ( 1879) to the chronicle of Wartenberg has direct note, that “the land of Saule ( Soule) is Raden near Bauska, named Saule in Lettish”.