An Etymological Dictionary of Astronomy and Astrophysics

A prefix which means being at or near the middle point of; being or occupying a middle place or position.

Etymology (EN): M.E., from O.E. midd-,
cognate with O.H.G. mitti, O.N. mithr,
Gothic midjis, O.Ir. mide, L. medius,
Gk. mesos, Skt. mádhya-, Av. maidiia- “middle, the middle,” Pers. miyân, as below.

Etymology (PE): Miyâni, from miyân “within, between, center,” from Mid.Pers. mayân “middle; among, between,” Av. maidiia- “middle, the middle,” maiδiiāna- “middle, center,” maδəma- [adj.] “middle, being in the middle; middling, of a middling size or quality,” maiδim “in the midst of,” cf. Skt. mádhya- “middle, located in the middle;” O.H.G. mitti “located in the middle.”
nim-, nimé, → half.