the.com/estrus

means The recurring period in female mammals when hormones peak and the body is biologically ready and receptive to mating.

from From Latin 'oestrus,' meaning gadfly or frenzy, itself borrowed from Greek 'oistros' — a word for the sting of a gadfly that came to mean any maddening, driving passion. The Greeks used it for the wild, goading urgency of desire itself; science later narrowed that ancient word for frenzy into a precise biological term for the fertile window.