Imitative term to describe a reserved, middle of the road type of laughter. Originated in the days before the internet on a BBS to represent how Beavis laughed on Beavis and Butt-Head. "huhu" was also used for Butt-head but did not catch on.
Also: hehehe, heh
leskhatyn: yeah, I tried sniffing coke once, but the ice cubes got stuck in my nose.