The use of confirmation names is a tradition among Catholic people in English speaking countries, in some German speaking countries and Poland, but it is completely unknown in most of the Catholic communities. It is not a Catholic rite, just a costum allowed by Church, like other costums in other countries/cultures: three names in the baptism, blessing of palms on Palm Sunday, blessing of animals on Saint Anthony's day, etc.
And about male names in nuns, there are two reasons.
The first one is the self humiliation. Chosing a male name, and to be called by it all the days the rest of her life, was a way to show humility and to abandon mundane trivialities and/or decorations (like hair, clothes, jewellery...) and a way to mortificate oneself (like to be barefoot, to use some devices as the cilicium...). It was just the same reason for some humility names among first Christians (Mucius, e.g.) or for some odd names among Puritans.
The second one is the devotion to a saint or to a prominent Catholic character, basically the Pople. That is why it was possible to find nuns named Sor María de San Andrés or Sor José and Sor Andrés and nuns named Sister JohnPaul.
The use of feminine names among monks is resticted, to my best knowledge, to related with Our Lady names or to Catholic misteries and faith matters, just like among the general population: Guadalupe, Rosario, Trinidad...