What does "velella" mean?

Velella: Any species of oceanic Siphonophora belonging to the genus Velella. Note: These creatures are brilliantly colored and float at the surface of the sea. They have an oblong, disklike body, supported by a thin chitinous plate, from which rises a thin diagonal crest which acts as a sail. The feeding and reproductive zooids hang down from the under side of the disk.