English
acrophase
From acro- + phase.
Proto-Indo-European *bʰeh₂- ‘to shine’
…
Proto-Hellenic *pʰáňňō ‘to appear’
Ancient Greek φαίνω ‘to bring to light; to appear’
Ancient Greek φάσις ‘appearance’
New Latin phasis
English phase
Today it means
noun The time period in a cycle during which the cycle crests or peaks, especially the upper part of a sine wave fitted to a measurement of a circadian pattern or other biological rhythm.
Language periods are conventional ranges, not dates for this word.
Etymograph / acrophase