From the word bissextus, which refers to February 29th.
Bissextus means literally “the second sixth,” so called because the 6th day before the first day of March in the ancient Roman calendar appeared a second time once every leap year.
EXAMPLES OF BISSEXTILE
The extra day in a bissextile helps keep the calendar in sync with the solar year.
February 29th is an occurrence that only happens in a bissextile.
Comes from the past participle of the Latin verb ܳ, “to shade.”
ܳhas the stem umbr(a), “shade, shadow,” also found in the Astronomy terms umbra, “the complete or perfect shadow of a planet,” and penumbra, “the partial or imperfect shadow outside the complete shadow of a planet.”
EXAMPLES OF ADUMBRATE
The subtle hints in her letter adumbrated her true intentions.
The cryptic message seemed to adumbrate a dark future for the kingdom.