[eesmith]

https://en.wikipedia.org/wiki/Paco says:

> Paco is a Spanish nickname for Francisco. According to folk etymology, the nickname has its origins in Saint Francis of Assisi, who was the father of the Franciscan order; his name was written in Latin by the order as pater communitatis (father of the community); hence "Paco" was supposedly obtained by taking the first syllable of each word.

https://es.wikipedia.org/wiki/Francisco has the same description, and comments that it's similar to how José is "Pepe" through "P(ater) P(utativus)", the husband of Mary, the father of Jesus. It then adds "[cita requerida]" to that description.

https://spanish.stackexchange.com/questions/17631/why-is-pac... mentions that one, and adds another possibility; writing "Phranciscus (the latinised version of Francisco de Asís's nickname) as Ph.co in signs and inscriptions", thus becoming "Paco", "Pacho", and "Pancho".

That cites http://www.alsurdelafrontera.es/2015/02/como-se-llega-de-fra... which cites Diccionario del origen de las palabras by Alberto Buitrago and J. Agustín Torijano.

[slim]

I know that when romans invented latin they transliterated greek letter Φ to P. So I checked the name written in greek and sure enough it could be abbreviated as paco if you don't know how to pronounce it : Φραγκίσκος

[cafard]

But isn't Beppe an Italian nickname for Giuseppe?

[eesmith]

I'm way out of my depth, and it appears to be full of folk etymology.

http://spanishlinguist.us/2013/03/pepe-and-paco-2-mysterious... says Real Academia España says Pepe comes from Beppe and there is no support for the "pater comunitatis" origin for Paco.

There is much discussion in the comments.

[borroka]

"Beppe" and the less used "Beppo" are both diminutives (not nicknames) of the popular (especially back in the day) biblical name Giuseppe. "Chicco" is an interesting case in Italian, as it is more of a nickname than a diminutive (hypocoristic, to be precise), and it can be used for the full names Francesco, Enrico, or Federico.