Many people do have 2 names:
a jewish name and
a civil name.
These people are mostly called on an everyday basis by the civil name.
When one is sick R”L what name should be used when davening for him?
only the jewish name?
the jewish name first followed by the civil name?
the civil name followed by the jewish name?
To add a last question if someone has no jewish name should we use his civil name only?
Can you please provide with references?
So far I haven’t found.
It is preferable to use both names, with the Jewish name first, followed by the civil name. A person that doesn’t have a Jewish name, then we use only his civil name, because that is his name.
Shulchan Aruch E:H 129-5,14, Bais Shmuel ibid 9, Shemos Ba’aretz pg. 118.