An axis is one of the reference lines a graph is measured from. The x-axis, the vertical axis, label the axis.
The horizontal one is conventionally x and the vertical y, and choosing where an axis starts is the commonest way to make a chart mislead without lying. An axis is also the line a thing spins about: the earth's axis, tilted about 23 degrees, which is what gives us seasons. Note the plural axes, spelt like the plural of axe; and the Axis powers, which is a political sense from the 1930s.
1nounaxisA reference line a graph is measured from.
“Put the dates along the horizontal axis and the prices up the vertical one.”
2nounbodyThe line a body spins about.
“The earth's axis tilts by roughly 23 degrees.”
Too few real examples of this word to estimate which sense is commonest.
axis is a reference or rotation line.
Latin axis means an axle. English axle is the inherited native form of the same Proto-Indo-European root, so the borrowed word and the homegrown one are cousins.
Proto-Indo-European
*h₂eḱs-
Latin
axis
English, today
axis
Borrowed from Latin axis. Borrowed from Latin axis (“axle, axis”) in the 16th century. Via Latin cognate with ala, aisle, atelier. Via Proto-Indo-European h₂eḱs- cognate with inherited English axle and borrowed axo-, axon.
Etymology from Wiktionary, CC BY-SA