Etymology
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perigee (n.)

"point at which a celestial body is nearest the Earth," 1590s, from Modern Latin perigeum (15c.), from Late Greek peregeion, used by Ptolemy as a noun, properly neuter of adjective perigeios "near the earth," from peri ges, from peri "near" (see peri-) + ges, genitive of "earth" (see Gaia). Now only of the moon, formerly used also for the corresponding point in the orbit of any celestial body. Compare apogee.

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apsis (n.)

"perigee of the moon, perihelion of a planet" (plural apsides), 1650s, from Latin apsis "arch, vault" (see apse).

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