This Greek flower and mythological choice doesn't make it into the pantheon of possibilities because of its association with narcissism. But narcissa is December's flower of the month, so Narcissa and Daffodil theoretically make perfect names for December babies.

Mythological young man who fell in love with his own image: the first narcissist.

A floral name from Greek myth, where it belonged to a nymph. It is also the name of a pretty herbaceous shrub with lilac flowers, commonly known as lily turf.