When did the middle finger become offensive? Apparently this symbol went far back to Roman Empire era. Back then it was called: digitus impudicus - the shameless, indecent or offensive finger. It actually the symbol of erect penis (the middle finger) and the other fingers are the symbol of the testicles. This symbol even surfaced in BC years.
Read more in http://www.bbc.co.uk/news/magazine-16916263