You might not be aware of it but it is indeed a common usage in both Dutch and Flemish, especially in the diminutive.
Phemist's tongue-in-cheek remark drew attention to it to suggest that the name might not be well chosen for those parts of the world.
See sense 2.2 here: http://www.vandale.nl/opzoeken?pattern=kwak&lang=nn
Or just google it (nsfw).
