Isn't it strange how widely accepted the term is? Everytime you hear someone say "that sucks" on TV, they are essentially saying "that sucks dick."
Dave: Frig off, Timmy - you are so gay.
The early Jazz musicians would say that a guy could really "Blow" if he had a good sound when playing the horn. If he couldn't play very well then they would say that he was "Sucking" on that horn. That's where the term "Suck" as being something bad came from.
He doesn't blow, he sucks.
Billy- "Went on Urban Dictionary and looked up words like 'sucks' and 'dick'."