axletree

[ak-suh l-tree] /ˈæk səlˌtri/
noun
1.
a bar, fixed crosswise under an animal-drawn vehicle, with a rounded spindle at each end upon which a wheel rotates.
Origin
1250-1300; Middle English; see axle, tree
British Dictionary definitions for axletree

axletree

/ˈæksəlˌtriː/
noun
1.
a bar fixed across the underpart of a wagon or carriage that has rounded ends on which the wheels revolve