Regional slang assumed to be derived from 'Moody' originating from Derby, and over recent years having gradually become more commonly used as far south as Northamptonshire and as far north as Manchester (in many episodes of Coronation Street for example).
It is used most widely to describe children when they are having a tantrum or an adult who is sulking when not getting their own way. It describes a person who is feeling sorry for themselves or is crying shallow, crocodile tears.
This fantastic adjective has risen to more widespread fame in recent times thanks to those lovely lads from Sheffield, the Arctic Monkeys who wrote a song called Mardy Bum about a girl who was really mardy. Now all those southern softies have latched onto this fantastic word, it won't be long before we are hearing Peggy Mitchell behind the bar of the Queen Vic calling Billy a 'Mard Arse'.
In Derby, where the word originates from, it is very common to hear people calling others 'Mard Arse'. 'Stop bein such a mard arse!' meaning 'Stop being so moody, childish, grumpy, etc'.
The word is also used commonly in playground banter. Rhymes such as 'Mardy Mardy Mustard, You Can't Eat Your Custard, Nah, Nah, Nah, Nah, Nah!' were commonplace in Derby schools during the 1980s.
What is so wonderful about this word is that it has a whole meaning of its own and even though assumed to be derived from 'moody' it is not quite the same.
It is therefore of interest to know that the Chinese have a word that has exactly the same meaning as 'Mardy', therefore, it should be accepted into the Oxford English dictionary as a recognised word.