A lot of my nicknames are usually references to other games, anime, or even mythology. Anyways, the nicknames I've given to my Y team were...
Claire (Delphox) - I had to soft-reset at least ten times for a female Fennekin, just so I can give her this nickname. The name originated from the character Claire Elstein from Seirei Tsukai no Blade Dance, in which she was a tsundere fire mage. I just thought Delphox seemed to have a lot in common with Claire, so I decided to name her that.
Meruru (Azumarill) - Just named here off the character Meruru from Atelier Meruru, LOL.
Bridget (Sylveon) - Named after the character Bridget from Guilty Gear, who was a guy that looked a lot like a girl. So, same thing here. My Slyveon, although looks feminine was a male.
Laguna (Venusaur) - Named after Laguna from FF8. Also a shout out to a past Nuzlocke run of mine.
Tana (Salamence) - Named after Tana from FE:SS, who was a Pegasus Knight that can promote to a Wyvern Knight. Also, my Salamence was female which really helped in picking this name.
Shyvana (Garchomp) - Named after the LoL Champion, Shyvana! Although, my Garchomp didn't breath fire, she was still a wreckage machine like Shyvana is.
Jormungandr (Gyarados) - Named after the Ouroboros of Norse Mythology, Jormungandr. Honestly, there is not much reasoning behind this name as it was just from the top of my head.
Ragna (Absol) - Named after Ragna the Bloodedge from Blazblue. Both have the colour of white on their body somewhere, and both possess sword like things.
Chrom (Heracross) - Named after FE: Awakening's Chrom. Although, Heracross doesn't use any slashing type attacks, the blue colour scheme of his just reminded me of Chrom.
Kefka (Exeggutor) - Named after FF6's Kefka. Exeggutor's faces seemed to be like a form of crazy that just reminded me of the maniacal Kefka.
Peashy (Raichu) - Name used to be Neptune before I changed it. Her first nickname Neptune was just a randomish name I gave her. I renamed her Peashy since I thought Raichu's yellowish colour scheme fits the name Peashy better than Neptune. Either way, both names came from the characters Neptune and Peashy from Hyperdimension Neptunia.
Axel (Talonflame) - Named after the hot-head Nobody Axel from KH2.