Meaning

noun third mast from the bow in a vessel having three or more masts; the after and shorter mast of a yawl, ketch, or dandy

noun fore-and-aft sail set on the mizzenmast

originFrom Middle English mesan, meseyn, myson, from Middle French misaine, modified from Old French migenne (through influence from Italian mezzana), from Old Catalan mitjana, feminine of mitjan, ultimately from Latin medianus. Doublet of mean and median.

Etymology from Wiktionary, CC BY-SA 3.0