When DGD was about 3 and a bit she went to the loo and when DH asked, from the other side of the door, what was taking so long (he wanted to go) she said she was having a safety poo.
DH wasn't sure what she meant by a "safety poo" he asked her what made it different from any other time.
Big sigh "well mummy is talking to granny and she'll be ages so I thought I'd have a safety poo because if mummy is in a hurry I have to have an urgency poo"
OK said OH, still not sure what DGD was talking about but carried on trying to get some clarity.
Her reply was "it's like when we are going out, mummy tells me to have a safety wee even if I don't feel like having one. Because she doesn't want to have to find somewhere when we are out for me to have an emergency wee"
"So, more sighs, mummy will be talking for ages and won't be hurrying me up I thought I'd have a safety poo."
Simple really wasn't it :-)
How many of us can remember saying to out children about "go before you leave" :-) Funny the different way children make sense of what we tell them.