English
ferning
From fern + -ing.
Formed from fern + -ing
Proto-Indo-European *p(t)erH-
…
Proto-Germanic *farnaz
Proto-West Germanic *farn
Old English fearn
Middle English fern
English fern
Today it means
noun A characteristic fern-like pattern on a slide viewed under low power on a microscope, used as a sign when testing for ovulation or the presence of amniotic fluid.
Language periods are conventional ranges, not dates for this word.
Etymograph / ferning