This is an Acronym that originally meant "Silently Masturbating During Homework". It was converted into "Shaking My Damn Head" when a Facebook
member who often used this term was asked, "What
does that mean?". The individual responded
with a quick and witty
answer. "Shaking My Damn Head". The individual
who asked what SMDH
, "You sure do shake your damn head a lot".