A Slither Of Cake

Something perturbs me. In the 3 years that I've been in Sydney, I've heard all my colleagues without fail, from the 21 year old, part-time uni undergrad to the 45 year old corporate veteran, ask for a "slither" of cake. I told the 21 year old at that time that it was a "sliver" of cake and snakes slither. That seemed to be new information to her.

Fast forward 3 years - 2 days ago, the team supervisor also asked for a "slither" of cake as we eyed the generous wedge of creamy Black Forest birthday cake that our neighbours brought over to share.

Now, were several generations of Australian school children taught wrongly by ALL their teachers? Or is this a cultural faux pas? Or do they all have a (selective) lisp?