Kaywinnet

Kaywinnet Lee Frye was a character in the television show, Firefly, and it's movie sequel, Serenity. She was commonly known by the nickname Kaylee. She was the ship's mechanic. Kaylee was sleeping with the Serenity's mechanic, who could not fix Serenity. When Kaylee showed Captain Reynolds that the ship could be fixed, he gave her the mechanic's job. She was in love with Simon Tam.

The name appears to have been invented by Joss Whedon. It could be a combination of Kay, and the surname Winnett. Kay is a short form of Katherine, which means 'pure'. The surname Winnett is derived from Winthrop, which comes from winn, meaning 'friend' and prop, which means settlement. So, a possible meaning could be 'pure friend'.

Kaywinnet has never appeared in the Social Security Administration's name database.

Inara

Inara Serra was a character on the short lived television show Firefly, and it's subsequent feature film, Serenity. Inara was a licensed courtesan to the wealthy, referred to as a Companion. Her services went beyond the physical, and she helped with her client's emotional well-being as well. She leased one of Serenity's shuttle craft which she used to travel to meet clients. Although it was not mentioned in the series or the movie, behind the scenes information revealed that Inara had a terminal illness. 

Inara comes from a deity in Hittite mythology. She was the goddess of the wild animals of the steppe. She was a protective deity, and was involved with the Puruli spring festival. In the Greek pantheon, she was known as Artemis. Some name websites claim that Inara is of Arabic origin and means 'Ray of Light' or 'Heaven sent', but I can't find much else to back up that claim. In 2011, the name Inara was given to 108 girls in the United States.

River

River Tam was the younger sister of Dr. Simon Tam on the series Firefly. She was a prodigy, and was sent to a private school which turned out to be a government experiment in creating the perfect assassin. After decoding a secret message she sent to him, Simon rescued her, and they both became fugitives. They took refuge on Serenity, with Simon becoming the ship's medic. Due to the experimentation on her mind, River had violent outbursts of emotion and psychic abilities. She was also incredibly skilled in hand to hand combat, performing in ways that no normal human could. 

River Song was a character in the modern version of Doctor Who. River was actually named Melody Pond, and was the daughter of Amelia Pond and Rory Williams. Melody's name was translated to River Song by Lorna Bucket of the Gamma Forest. Pond wasn't translatable because the only water in the forest was the river. River was kidnapped as an infant and trained to kill the Doctor. She escaped and grew up alongside her parents as their childhood friend. She and the Doctor kept meeting each other out of order, and she kept a journal of their meetings. She spent much of her time in prison, which she routinely escaped from and returned to. She was imprisoned for killing the Doctor, although it ended up being just a replica of him. The first time the Doctor met her was when she died, having sacrificed herself to save others trapped in a Library computer. The Doctor saved her by transferring her consciousness to the computer where she was able to live forever in a simulation. 

In 2011, River ranked at #424 for boys, and was #913 for girls.