What does arbor mean?
The definition of arbor
Ar”bor, n.
Etym: [OE. herber, herbere, properly a garden of herbs, F. herbier, fr. L. herbarium. See Herb, and cf. Herbarium.]

A kind of latticework formed of, or covered with, vines, branches of trees, or other plants, for shade; a bower. Sir P. Sidney.

Ar”bor, n. [Written also arbour.]
Etym: [L., a tree, a beam.]

1 (Bot.)
A tree, as distinguished from a shrub.

2.
Etym: [Cf. F. arbre.] (Mech.)
(a) An axle or spindle of a wheel or opinion.
(b) A mandrel in lathe turning. Knight. Arbor Day, a day appointed for planting trees and shrubs. [U.S.]