Newcastle United fans were first labelled the Toon Army in reference to the Geordie pronunciation of the word "town" with the media subsequently adopting the name and championing it in reference to their fans.
It is a relatively recent nickname, coined because thousands of fans crowd the town centre before and after matches, most wearing the black and white shirts, which makes them look like an army. Newcastle is famous for its night-time clubbing culture and the locals say they are 'ganning out in the toon".
They are also called United and have not yet shed their original nickname of Magpies. That is also the nickname of Notts County, the oldest club in the Football League, who also play in black-and-white shirts.
All Geordies and those people who live in the North East , certainly in Tyneside and Northumberland and parts of Durham , refer to Newcastle 'the city' as 'The Toon'.And if you are to go out in the evening the expression , 'Im gannin doon the toon', would mean i am having an evening in Newcastle.So the natural follow on would be to call Newcastle fans , the 'Toon Army' , and this came to prevelence in Keegans first reign as manager where banners with 'Toon Army' were seem on national tv and the phrase ', Toon Army ', was used.However the reference to Newcastle being called the Toon goes back probably over a 100 yrs , as i recall my grandad using it , and i am 56.