A quick search shows that the name Silona exists in Germany, and more specifically as an East German name (all four hits come from the former GDR):
https://duckduckgo.com/?t=ffsb&q=Silona+site%3Astayfriends.de&atb=v344-1&ia=web
However, this search result gives no hints at the etymology of the name, the surnames are usual German names and don't hint on the origin.
EDIT: Found a Swedish ship named Silona that stranded near Hamburg during the North Sea flood of 1962, maybe the name of the ship deemed a suitable girl's name to some parents:
https://de.wikipedia.org/wiki/Silona
--elbowin
This message was edited 1/9/2023, 2:50 PM