English
intermenstrual
From inter- + menstrual.
Formed from inter- + menstrual
Proto-Indo-European *h₁én ‘in’
Proto-Indo-European *h₁entér ‘between’
Proto-Italic *n̥ter ‘between’
Latin inter ‘between’
English inter-
Proto-Indo-European *mḗh₁n̥s ‘moon, month’
…
Latin neuter
Latin mēnstrua ‘menses’
Latin mēnstruālis ‘of or pertaining to the monthly courses of women’
Middle English menstruall
English menstrual
Today it means
adj Between menstrual periods.
Language periods are conventional ranges, not dates for this word.
Etymograph / intermenstrual