How did the term French leave originate?

French leave primarily means taking leave without permission from work. Some believe it is meant to convey the act of leisurely desertion from a military unit. Being away on leave from one’s post or duties has its roots in the 17th century and does not so much have its origins in cowardice but in a French custom of leaving a party without saying goodbye or thanking the hosts. The term is still in use in the Indian Navy for sailors who overstay on land.