Since I’ve been living with a name Jesus for the last 30 years, I feel I can answer this question.
It is extremely common in Mexico for people to give diminutives/nicknames to names, some examples:
Francisco: Pancho/Paco
Mariano: Nano
Jose: Pepe
Salvador: Chava
Enrique: Quique
Josefina: Chepina
Jesus: Chucho
So it is very common to people named Jesus to be called by their families and friends Chucho, since its clearly not a diminutive (being longer than the original name), it gets reduced to ‘Chuy’ for simplicity/friendliness.
Note, sometimes the nicknames/diminutives of names have no relation at all with the original name, might be some pun/wordplay or the family just decided to call you that since young and it stuck.
Also note that in some parts of Mexico a “Chucho” is also another way to say dog.
Appendix:Spanish diminutives of given names
“Cristo Hijo Unico de Yahveh” (Crhist only son of Yahweh). This comes from Jesus Christ and the bible.For me it seems that the acronym came after the nickname and not before. But I don’t know for sure.
I can only point out that MANY common Spanish nicknames are formed by combing “Ch” with a syllable or syllables of the full name. “Chuy” is just one example.A girl named Isabel is often nicknamed “Chavela.” A guy named Ernesto is often called “Che” (it wasn’t just Senor Guevara!). That’s just a pattern within Spanish.To ask “why” is like asking “why do so many English nicknames seem to be rhymes for shortened versions of the full name
(“Bob” for Rob/ert,” “Bill” for Will/iam, “Ted” for Ed/ward, etc.)?” The reason is… there IS no reason. Things just evolved that way.
Most of the informal but very common nickname that mexican use, are part of the american-indian dialects. Even in the formal way Mejico is the correct way to spell the name but as part of our heritage we use the X and sounds more close to as the english speakers pronounce, for us this will sound like like sh (shine). because the name of the tribe was the mexicas (meshicas).
Some hypocorisms in medieval Spain end in “-uy” (“Ruy” for “Rodrigo”, “Guy” for “Wido”). The actual pronunciation of “J” was in flux during this period; today is a hard sound, but it used to be softer, closer to the way the digraph “ch” is pronounced today.
Also “Chuy” is close in pronunciation to the original hebrew “Yeshua”, probably due to ladino influence. “Jesus” path is longer, Latin and Greek are in the middle.
EXPAT in BAJA Mexico 