Sources for using the father's name when praying for a non-Jew

Question

Related to this answer.

Earlier today I was sent a video that showed the Chief Rabbis of Israel at the Kotel making a Mi Sheberach for the refuah of President Trump, where they called him דונלד ג'ון בן פרד (Donald John ben Fred). I was surprised that they used his father's name. The person who sent me the video told me that he thinks he heard that that's the halacha. After digging around here on MY, I found the above mentioned answer (and other answers for that question). The source appears to be the Lubavitcher Rebbe. Are there older sources? What is the reasoning?

Answer 1

Yeshiva World News reported that Rav Zilberstein shlita said to do so in the name of the Maharshal.

This was originally reported by Kikar Shabbat, who asked Rav Zilberstein and he responded as reported.

I searched all over and failed to find this Maharshal...

^{What I don't get is Donald Trump's father's name was Frederick. If they used Donald's full name why not also his father's?}

Answer 2

This isn't a source but it is an explanation for the reasoning. I ended up asking Chief Rabbi Lau what the deal was, and he explained:

a. The reason that they didn't use Trump's father's full name is because they didn't know it. 'Fred' was the name given to them by the ambassador. So, something of a hiccup on his part.

b. The reason they used his father's name and not his mother's name was because the din of "yichus" from the maternal side is only for Jews and not non-Jews.