let (something) slip (out)
to tell a secret by accident
I let the date of the wedding slip out by mistake at the dinner party.
Cutest Animal Facts
Greater hornbills make great dads
Most animals see mums working tirelessly to look after their babies, but not so with the Greater Hornbill. In fact, mum and dad work together to ensure they can provide the utmost care for their babies, splitting the duties and alternating who feeds the little ones on a daily basis.