Suomesta löytyy useita Rantasalo -sukuja. Sukunimi on usein otettu, kun nimiä on suomennettu. Esim: Björni > Rantasalo, Durchman > Rantasalo jne.
My grandfather had a surname of Karlsson, which meens son of Karl. During 1910 there were a tendency to get surnames in Finnish. A farm my grandparents were owing that time, had a name Rantasalo. A farm was located on the beaches of Lake of Päijänne ( county of Padasjoki, village of Mainiemi ) as it is today. Rantasalo Ranta= beach Salo= forrested area, not very much populated also most of the islands on the Lake of Päijänne has endings of Salo ex. Judinsalo, Kilvensalo, Haukkasalo, etc.
https://www.geni.com/projects/Suutari-Erik-Durchmanin-j%25C3%25A4lkel%25C3%25A4iset/31407 -projektissa on paljon Rantasaloja.