"Is it to do with the myth of Narcissus - the boy who fell in love with his own reflection?"

Narcissus
Public DomainNarcissus - Credit: John William Waterhouse

“What a man thinks of himself, that is which determines, or rather indicates, his fate.” - Henry David Thoreau

In Greek mythology, Narcissus was a beautiful young man who spurned the love of others for the adoration of his own image. According to Encyclopedia Mythica "A young man, Ameinias, was in love with Narcissus, but he rejected Ameinias' love. He grew tired of Ameinias' affections and sent him a present of a sword. Ameinias killed himself with the sword in front of Narcissus' door and as he died, he called curses upon Narcissus. One day Narcissus fell in love with his own reflection in a spring and, in desperation, killed himself."

Flowers that grew in the place where he died came to be known as Narcissus.

A narcissist is someone who has a tendency towards self-worship or a preoccupation or erotic interest in their own physical features.