In סימן דש, סקכ"ו the Mishnah Berurah says as follows:
במקום שהמלך יר"ה גזר שאין שום אדם...
My edition of Mishnah Berurah the acronym is expanded as: "יָרוּם הוֹדוֹ", which I believe means May his praise be heightened.
Is he referring to someone specific? Is this just a general honorific to give kings? I have yet to see this used. In the MB it says he's quoting רשד"ם and ריב"ל, not sure who they were or where they lived. In Shaar HaTziyun he cites this as מגן אברהם בשם הכנסת הגדולה.
A quick Google search brought me to the article of Franz Josef, the ruler of Austria in the late 19th, early 20th century. The Google result said he was referred to by Jews as הקיסר ירום הודו, but the actual article didn't have this information