late 14c., "intercalation, insertion of days into a calendar," from Old French embolisme "intercalation," from Late Latin embolismus "insertion of days in a calendar to correct errors," from Late Greek embolismos "intercalation," from embolos "insertion, a plug, wedge" (see embolus). Medical sense of "obstruction of a blood vessel" is first recorded in English 1855. Related: embolismic.