Plain and simple, this was started by the Mexicans. It's their way of saying "Man".. This is due to the Mexican accent converted to English. Now people say 'mang' because it's (1) different and (2) humorous.
"What's up, mang?"
Prices shown in USD.
邮件由 email@example.com 发出。我们决不会发送垃圾邮件。