It is a common "Christogram" based on the first three letters of the name of "Jesus" in Greek -- "IHΣOYΣ," thus rendered in Latin as "IHSOVS." It was later interpreted to mean "Iesus Hominum Salvator" or "Jesus Savior of Mankind." It is also the centerpiece on the seal of the Society of Jesus, an order of priests also known as the "Jesuits," among whom it has come to mean "Iesum Habemus Socium" ("We have Jesus as Companion") or "Iesu Humilis Societas" ("Humble Society of Jesus").
Hold that thought.
At a recent visit to Georgetown University, the White House asked that the backdrop of the location where the President would be speaking, one which featured the "IHS" Christogram, be covered while he was speaking there. The Jesuits -- who in the last forty years could never resist an opportunity to suck up to brokers of secular power -- granted this request, despite its unprecedented nature, and despite having no real obligation to do so.
After all, what was the White House going to do, cancel?
In Catholic tradition, the Holy Name is neither used nor dismissed lightly. In fact, outside of prayer, it is used sparingly. In the traditional Mass (and properly speaking, on all other occasions), at the mention of His Name, one shows the proper respect by a bow of the head. When the passage from St Paul's letter to the Philippians is read for the Epistle, and the reader proclaims that "at the name of Jesus, every knee shall bend," he and everyone else standing or sitting is directed to genuflect. When officiating in the sanctuary at the mention of His Name, a seated cleric tips his biretta, and those who serve the cleric bow to the crucifix. (Likewise, when outdoors, men will show respect by momentarily removing their hats.)
Sometimes I meet a sincerely motiviated parish worker who makes reference to the Blessed Sacrament being reserved in the Tabernacle -- and you know who your are, bless your heart -- by saying in passing that "Jesus is in there." Not that this isn't true, but we can't very well spend half our time bowing every time someone means well. That is why we have the proper substitutes, just as any great King has many titles for his many attributes. We don't say "Jesus is in the tabernacle." We say that "the Blessed Sacrament is reserved in the tabernacle." Or we refer to the Sacrament as "the sacred Host" or "the precious Blood," or in both forms collectively as "the sacred Species." (Haven't heard that last one in a while, have you?)
Then again, some of us use it when swearing, which is an affront to the Name, and a confessional matter. The Holy Name Society traces its roots to the Council of Lyons in 1274, as a means of reparation for offenses to His Name. Until recent years, it was the most common form of parish men's club.
We show proper respect, to the office of the President of the United States, by refraining from being on a first-name basis with him. His closest confidants will refer to him, publicly and privately, as "Mister President." It is a similar show of respect to Our Lord, that we revere His Name.
Unless you're either a Jesuit with someone to impress, or a public official who cannot return the respect he commands from others.
Or, in this case, both.