Chop-a-nose day

Someone asked me:

"There is a Mother Goose rhyme that reads:

My mother, and your mother,
Went over the way;
Said my mother, to your mother,
'It's chop-a-nose day.'

Perhaps you can answer this: Whatever is 'chop-a-nose day?' I think it has to do with satisfying one's curiosity, but that's just a guess."

You grab a kid's nose with your thumb and chop off his nose with your other hand--my always falling down Uncle Dave used to do this all the time.
He would come over and say "Today is chop a nose day" causing me and my brothers to run and hide.

Thanks!