Can't always trust the Interpreter

One chapter in my nursing career involved visiting local plants and providing Flu shots to the line workers. Many at this plant were Hispanic. After setting everything up I told the Line Supervisor (also Hispanic) " Ask them to line up and pull up the sleeve of their shirts so I can easily get to the (Deltoid) muscle". He announced something very loud. The next thing I knew all the line workers were laughing, undoing their belts and pulling their pants down! I said to the line Boss "Whoa, whoa...arm! Not butt!" He burst out laughing and said "I know. I just wanted to mess with them".