What is "kauila"

Kauila refers to two species of trees in the buckthorn family, Rhamnaceae, that are endemic to Hawaii: Alphitonia ponderosa and Colubrina oppositifolia. Their wood was prized for being extremely hard, and is so dense that it sinks in water. Both occur in dry to mesic forest and are now rare; C. oppositifolia is listed as Endangered.