Iolanthe (Ἰολάνθη) comes from the Greek ion (violet) and anthos (flower) — meaning "violet flower." The name was popularised by Gilbert and Sullivan's 1882 comic opera Iolanthe, about a fairy who marries a mortal.
Iolanthe remains rare but distinctive. The name shares roots with Iolanda (Italian/Portuguese), Yolanda (Spanish), and Violet — all from the same Greek floral source.
Iolanthe reduces to one — the number of singular violet bloom.