Seungyeon shared the stories behind her pets’ names and revealed 'Nanan' was actually Jeongyeon’s nickname when she was little because she especially liked Nana from Teletubbies.
Nanan resembled Jeongyeon a lot when she first came into the family so Nanan became her name
If you asked little Jeongyeon what her name was she would shout 'Nanani!' so that became her nickname throughout her childhood. Seungyeon says that might be why Nanan likes Jeongyeon the most