Lissuin

Lissuin was a fragrant flower brought by the Elves from Tol Eressëa to Númenor. Its fragrance was said to bring heart at ease. Along with elanor, Lissuin was adorned on a ship to grace the wedding of Aldarion and Erendis.

Etymology
The term Lissuin might somehow be related to the Quenya term issë ("sweet").