Hummer is a brand of trucks sold by Motors Liquidation Company (the company left over from General Motors' bankruptcy, aka the old GM). The original Hummer H1 was based on the military High Mobility Multipurpose Wheeled Vehicle (HMMWV, or Humvee). However, the Hummer H2 and the Hummer H3 were based on other, smaller civilian-market vehicles. Chinese automaker Sichuan Tengzhong Heavy Industrial Machinery Company announced in 2009 that it will acquire the Hummer brand pending government approvals.
Source : http://en.wikipedia.org/wiki/Hummer