It would be under Constantine the Great that Christianity would become a legal religion throughout the Roman Empire, causing the church to explode in both size and popularity.

There are several variations of the Chi Rho. 2. The Chi Rho is sometimes shown with the letter “N”. What word the “N” represents is up for debate. It could be the word nika meaning “to conquer.” The meaning of this symbol would be “Christ conquers.” It could also be the word Noster meaning “our Lord.”
In this case, the symbol would read “Christ our Lord.” 3. The Chi Rho can also have the letter “I” added. This is simply the adding of the next letter in “Christos.” 4. The Chi Rho is often combined with the Ihs monogram to form some interesting and beautiful combinations. The combined monogram reads “Jesus Christ.”

DEXTRA DOMINI – Latin for “the right hand of the Lord.” It always accompanies an image of a hand.

DOMINUS NOSTER JESUS CHRISTUS – Latin for “Our
Lord Jesus Christ”.

ECCE AGNUS DEI – Latin for “behold the Lamb of God.” This exclamation was said by John the Baptist when he saw Jesus approaching him (John 1:29).

ECCE HOMO – Latin for “behold the man.” This exclamation
was made by Pontius Pilate as he presented Jesus to the Jews (John 19:5).