I never got it but I always thought it was pretty damn funny when someone did. When I'd find out I would rag their asses and not let them have a minutes peace until the work day was done. I cut them no slack. I would shout: Hey, Gangway here comes The VD Boy!
And all the troops would point at him and laugh!
Rarely did a "VD Boy" ever get the clap again in my platoon.