The story
From being a skateboard with an additional degree of freedom of movement (yaw) and some additional rocking (roll) movement.
Etymology from Wiktionary, CC BY-SA 4.0.
freeboard
Today it means: The vertical distance between the waterline and the uppermost watertight deck of a vessel, or the vertical distance from the waterline up to the top of the gunwale (of an open boat). Full definition →