English
heterosphere
From hetero- + -sphere.
Proto-Indo-European *sperH- ‘to kick, rebound, move convulsively’
…
Latin sphaera ‘ball, globe, celestial sphere’
Late Latin sphēra
Old French sphere ‘sphere (shape)’
Middle English spere ‘the cosmos, outer space’
English sphere
Today it means
noun The upper part of the atmosphere, above about 60 miles or 100 km, in which there is great variation in its composition.
Language periods are conventional ranges, not dates for this word.
Etymograph / heterosphere