1540s, "imaginary straight line around which a body (such as the Earth) rotates," from Latin axis "axle, pivot, axis of the earth or sky," from PIE *aks- "axis" (cf. Old English eax, Old High German ahsa "axle;" Greek axon "axis, axle, wagon;" Sanskrit aksah "an axle, axis, beam of a balance;" Lithuanian aszis "axle"). Figurative sense in world history of "alliance between Germany and Italy" (later extended unetymologically to include Japan) is from 1936. Original reference was to a "Rome-Berlin axis" in central Europe. The word later was used in reference to a London-Washington axis (World War II) and a Moscow-Peking axis (early Cold War).
axis ax·is (āk'sĭs)
n. pl. ax·es (āk'sēz')
A real or imaginary straight line about which a body or geometric object rotates or may be conceived to rotate.
A center line to which parts of a structure or body may be referred.
The second cervical vertebra. Also called epistropheus, vertebra dentata.
An artery that divides into many branches at its origin.
An imaginary straight line passing through the North Pole, the center of the Earth, and the South Pole. The Earth rotates around this axis.
In geometry, a straight line about which an object may rotate or that divides an object into symmetrical halves.
Note: The axis of the Earth is an imaginary line drawn through the North Pole and the South Pole.