lingum is sanskrit for emblem/symbol. shiv lingum means the sacred mark of shiva. The full word runs as "Jyothirlingam" means the Lingam in the form of jyothi, i.e. the flame. If you see any candle burning, the flame gets an oval-cylyndrical shape and Shiva or Mahakaal could not be given any face and the people started making the shape of the "jyothi" or the light.
Over the years, invaders and non-Hindus converted the same and used it for their advantage and also many Hindus are to blame for this, as they have failed effectively in countering this propaganda.
PS Please dont think that lingum in this case means sex organ
Your abusing me does not change that - Muhammed is the BIGGEST ABUSE ! Now do u have any answers for my queries ?