The hyacinth is a flowering plant in the family of Asparagaceae, meaning it’s related to the fancy vegetable that makes your pee smell funny - rest assured, hyacinth flowers are fragrant, but not in that way. In fact they’re pretty renowned for their scent - which vary between different colours and change over the course of the flowering season - and are used commonly in perfumes by everyone from Burberry to Vivienne Westwood.
FOTW has been running long enough though that I know what you’re really here for: tenuous or arbitrary folklore that gives the plant it’s name. Fear not, because as usual the Ancient Greeks have got you covered! In literary myth, Hyacinthus was the young lover of Apollo (supposedly they were the first ever gay lovers...sure). Hyacinthus was also lusted after by another god though, known as ‘West Wind’. One day Hyacinthus and Apollo were playing catch with a discus when jealous West Wind decided to ‘blow’ the wind in such a way that the discus struck Hyacinthus in his head, killing him. Grief-stricken Apollo made a (you guessed it) flower from his spilled blood, and the tears of Apollo stained the petals with his grief (this is from Ovid’s account, and actually quite moving).
That’s why as well as being a symbol of the Spring Equinox, the hyacinth is also known as ‘the sorrow flower,’ and ‘flower of the rain.’