An Etymological Dictionary of Astronomy and Astrophysics

1. In several → lunisolar calendars, an → intercalary month employed to preserve a seasonal relationship between the Lunar and Solar cycles. For example, in the → Hebrew calendar the extra month,
   called Adar Alef, was inserted after Shvat
   so that the month of Nissan (month of spring) does not begin in winter.
   

2. In ancient Iranian → solar calendar the additional whole month of 30 days employed every 120 years to compensate for the left-over quarters of days in a calendar year of 365 days (120 years × 0.25 days = 30 days).

Etymology (EN): M.E. embolisme, from M.L. embolismus “intercalation,” from Gk. emballein “to throw into, to insert,” from em- “in”

• ballein “to throw” (source of the medical term embolism “the obstruction (of an artery, etc.) by a clot of blood, bubble of air, etc.”); → month.

Etymology (PE): Behizak, from Mid.Pers. vihezagig or vihezakik
“movable,” from vihezag “movement, progression,” from vihez- “to move, progress;” mâh, → month.