The natural progression of language by means of:
1.) Abbreviation (bro from brother)
2.)
Word reversal (cool and hot for good)
3.) A need for secrecy (dime
bag for $10 of pot or 1/10oz of weed)
4.) Degree of separation (green for marijuana)
5.) Expressed honorific (calling a close
friend your brother)
6.) Combination (Branjalina for Brad Pit and Angelina Jolie)
7.) Any other
word not recognized by the major dictionaries as viable, but which a large portion of the population will understand the meaning of.
Though he did not allow slang to be used in his classroom, Prof.
Smith was known to
call his students "dude", "man", and "bro"
outside of class in a feeble attempt to regain some of his lost youth.