In many countries new parents are allowed to take legally protected time off from work to stay at home with their baby. Until the late 1990's this was only applicable to women not men.
Many men now partake in manternity to make it look like they are equal partners in the birthing/parenting process. In most cases it is a great way for men focus on beer drinking and daytime television.
It is seen as one of the only benefits single men are jealous of when looking at their married with children compatriots.
There will be a run on the beer stores as Billy is about to take another round of Man Ternity for his 3rd child.
I can't believe that lazy bastard will be taking Man Ternity leave-his wife doesn't even work.
Boys - stay as long as you want... I'm on Man Ternity and have nothing to do.