The name is from a bookseries called A Song of Ice and Fire by George R R Martin. The Boyfriend is a little more than obsessed with it. This is what Wikipedia says about Arya Stark:
Arya (a POV character) is a skinny, athletic girl with an interest in fighting and exploring. She is plain of face, resembling her father and her half-brother Jon Snow, and she is often mistaken for a boy. She is a foil of her sister Sansa, whom she often describes as "stupid." Throughout her travels Arya displays great resourcefulness, stealthy cunning, and a certain grim toughness that develops especially after her father's execution.
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Arya Stark is brave etc, and it just fitted the little kitty so well.