What does "laburnum" mean?

Laburnum: A small leguminous tree (Cytisus Laburnum), native of the Alps. The plant is reputed to be poisonous, esp. the bark and seeds. It has handsome racemes of yellow blossoms. Note: Scotch laburnum (Cytisus alpinus) is similar, but has smooth leaves; purple laburnum is C. purpureus.