Doing a 'Bally'

When someone is doing a 'Bally' they are generally not coming into work because they have a minor sniffle - or in most cases there is nothing wrong them at all, and they had simply heard another person in the work place was unwell, and decided to jump onto their bandwagon.

Person 1 - "Have you seen Woody today?" - Person 2 "He's not in, he's doing a 'Bally'"