The name is derived from the duck like sound emitted from the voice box of this particular form of life.
Almost every single Quacker is into the fantasy tabletop game Warhammer, and recently Warhammer Online Age of Reckoning.
Any sane man would respond, "I believe we have entered a pond my friend, because of all these damn quackers!"
Slang Usage - A quacker also applies to any molestation of female ducks including but not limited to a human male twisting his sausage into a counter-clockwise spiral in order to insert into a female ducks spiraled vagina.
Seriously, female ducks have spiraled vaginas…look it up.
What did you do, eat some Peeps or make a BBQ Pringles duck-bill?!
Ted – Uhh….neither. Mary is my pet duck. I twisted my yank into a spiral and banged her duck vagina.