Merriam-Webster's Collegiate® Dictionary, 11th Edition
ARBOR
I. noun
Etymology: Middle English erber, herber garden, from Anglo-French, from herbe herb, grass
Date: 14th century
a shelter of vines or branches or of latticework covered with climbing shrubs or vines,
II. noun
Etymology: Latin, tree, shaft
Date: 1659
a spindle or axle of a wheel, a main shaft or beam, a shaft on which a revolving cutting tool is mounted, a spindle on a cutting machine that holds the work to be cut