Chi Rho Meaning: The X and the P That Mean Christ
It looks like a P with an X through it. It is the name of Christ, it was painted on the shields of an army, and it is older than the crucifix as a public Christian sign.
What the Chi Rho means
The Chi Rho, ☧, is the first two letters of the Greek word for Christ, ΧΡΙΣΤΟΣ, Christos. Chi is the Greek letter that looks like an X. Rho is the Greek letter that looks like a P. Put one on top of the other and you have a monogram of the title Christ, the Anointed One. Like IHS, it is not an acronym. It is a name, shortened.
Constantine and "in this sign, conquer"
In the year 312 the emperor Constantine was about to fight his rival Maxentius for Rome at the Milvian Bridge. The early Christian writer Lactantius says Constantine was told in a dream to mark the heavenly sign of God on his soldiers' shields, and he did. Eusebius, writing later, tells it as a vision in the sky with the words in hoc signo vinces, in this sign you will conquer, and describes Constantine's battle standard, the labarum, topped with the Chi Rho. Constantine won. The next year Christianity was legal across the empire, and the Chi Rho went from the catacombs onto coins, helmets and banners.
In hoc signo vinces
In this sign you will conquer.
Alpha and Omega
You will often see the Chi Rho with an A on one side and an ω on the other. Those are alpha and omega, the first and last letters of the Greek alphabet, from Revelation 22:13: I am Alpha and Omega, the beginning and the end, the first and the last. Christ at the start, Christ at the end, Christ in the middle.
Where you still see it
On altar cloths and vestments, on the Easter candle, carved into old churches and Roman sarcophagi, and on a lot of gravestones. It is also why "Xmas" is not a war on Christmas. The X is the Greek chi, the first letter of Christ, and Christians have abbreviated His name that way for well over a thousand years.
Why it fits what we make
The Chi Rho is the original Christian streetwear: a mark painted on shields by men walking into a fight. That is the same instinct behind Saints Go Hard, St. Michael with the sword and St. George with the lance, and behind the flared cross on The Standard. If you want the Latin prayer of protection that goes with it, read Vade Retro Satana.
"I am Alpha and Omega, the beginning and the end, the first and the last."Revelation 22:13