In Japan, where Rambo was indeed very popular, the word "rambo" can be translated as "senseless violence"
Likewise, in Finland, "Rambo" has become a generic word to describe a commando of any sort. So much so that many younger people are surprised to find out the word comes from the movies instead of the other way around.
In Taiwan, any knife with a serrated blade back has come to be called a "Rambo Knife".
Rambo is in fact named after a US Postal Service worker, who also went on to cultivate a type of apple that now bears his name.
His first name comes from the war song "When Johnny Comes Marching Home Again".
Actually, just about every Hollywood A-lister was considered for the role at one time or another (it was in Development Hell for years). And Kirk Douglas was attached to direct at one point.