3rd June 2008 :: Under lock and key

“Here. Guard this with your life. The future of the entire country depends on it”
“OK, I will keep it locked and make sure no one gets hold of it.”

A few days later

“Can I get the documents I gave you. Quick”
“Sure, I'll be back in a jiffy with a locksmith”
“A locksmith?”
“Yes. To open the lock... don't you remember I told you I will keep it locked”
“I remember, but I don't remember you telling me that you will need a locksmith to open the lock... ”
“I guess it was obvious enough. If I meant to say I would have the key as well I would have said 'I 'll keep it under lock and key' instead of saying 'I'll keep it locked'.

This is how the term “keep it under lock and key” was invented. Just to make it foolproof.