English
Mesozoic
From meso- + -zoic.
Proto-Indo-European *médʰi ‘with, among’
Proto-Indo-European *médʰyos ‘middle’
Proto-Hellenic *métsos ‘middle’
Ancient Greek μέσος ‘middle’
English meso
Proto-Indo-European *gʷeyh₃- ‘to live’
…
Ancient Greek ζωός ‘alive’
Ancient Greek ζώῐ̈ον ‘Ionic form of ζῷον (zōîon)’
Ancient Greek ζῷον ‘animal’
Ancient Greek ζωϊκός ‘of or pertaining to animals’
English zoic
Today it means
adj Of a geologic era within the Phanerozoic eon that comprises the Triassic, Jurassic and Cretaceous periods from about 230 to 65 million years ago, when life on earth was dominated by reptiles.
Language periods are conventional ranges, not dates for this word.
Etymograph / Mesozoic