Vietnamese.
"The veteran viet officer spoke to his fellow soldiers in fluent English during the briefing."
South Vietnam, North Vietnam, or Vietnam entirely.
"The historical maps clearly distinguish between the regions of viet known as North and South before reunification."
The word viet was borrowed directly from the Vietnamese language to refer to a specific type of boat or watercraft used in that region. It entered English as a loanword without undergoing significant changes to its original meaning related to local maritime vessels.