Hyacinth is from the Greek hyakinthos — both the botanical name for the fragrant spring bulb and the name of a beautiful Spartan youth in Greek myth. Hyakinthos, the male lover of Apollo, was accidentally killed by a discus thrown by the god (or by the jealous wind Zephyrus); from his blood Apollo grew the first hyacinth flower. Hyacinth Bucket (pronounced "bouquet") is the heroine of the BBC sitcom Keeping Up Appearances (1990-1995). Saint Hyacinth (Jacek Odrowąż, 1185-1257) was a Polish Dominican friar.
Hyacinth does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Hyacinth reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.