In English when we conceal a smile, we sometimes use the expression ‘to laugh in my sleeve’. This is the approximate meaning of ‘att le i mjugg’. Most Swedes, however, don’t know what ‘mjugg’ means as it is a rather odd word.
‘Mjugg’ is an old word which was first noted in the 1500’s. Meaning ‘in secret’, or ‘on the sly’, it is thought to either come from German or English. The German word ‘mucken’ means to smile or mumble. An old English expression ‘hugger-mugger’ meant clandestine. In regional Swedish, the word ‘mugg’ exists – meaning ‘in secret’.
So, ‘att le i mjugg’ means ‘to smile in secret’, probably with contempt and at somebody else’s expense.