Arbor
'ARBOR, noun [Latin arbor a tree, and the primary sense.]
1. A frame of lattice work, covered with vines, branches of trees or other plants, for shade; a bower.
2. In botany, a tree, as distinguished from a shrub. The distinction which Linne makes, that a tree springs up with a bud on the stem, and a shrub not, is found not to hold universally; and the tree, in popular understanding, differs from the shrub only in size. arbor forms the seventh family of vegetables in Linne's system. [See Tree.]
3. In mechanics, the principal part of a machine, sustaining the rest. Also the axis or spindle of a machine, as of a crane, or windmill.
This in America is called the shaft.