An Etymological Dictionary of Astronomy and Astrophysics

A combining form meaning “middle,” used in the formation of compound words; e.g.
→ meson; → mesosphere.

Etymology (EN): From Gk. mesos “middle, in the middle;” akin to L. medius, Pers. miyân, → middle; → medium.

Etymology (PE): Meso-, loan from Gk.