There are two trains of thought of it's origin. The first one is the word 'scally' is a
derivative of the Afrikaans word 'skollie' which means naughty or pesky
little boy - A lot of soldiers from Liverpool fought in the Boer War and Afrikaans words were in vogue in the Scouse dialect for awhile though only two remain which are 'scally' and spion kop'
The other
train of thought it that 'Scally' was derived from a tough Irish-Liverpool family of the same name, the Scally family had a lot of sons who were always
up to no good and thus the beginnings of the term Scally.
A scally is not from Birmingham, Leicester, Keighley, Corby, Brighton, Rotterdam or Dar es Salaam - Scallies are Scousers or Mancunian in origin, Scallies dress, act, talk and interact in a very individualistic way.
Scallies don't tend to work, they end to dress in sports/casual gear, they tend to be Irish Catholic in origin and they tend to smoke, drink take too many drugs.
Scallies are physically puny and tend not to be able to fight all that well - despite their violent tenedencies - they get round this by breeding pitbull terriers and walking them everywhere and carrying weaponary which they will use liberally.
Scallies tend to come from a long line of workshy, deviant, unemployable and violent
bloodlines and DNA. Despite this some scallies make it to
the big time in the sporting and musical fields - most noteworthy are the Gallagher brothers and Joey Barton - proper scalls them three.
The nearest cousin to the scally is the Glaswegian 'Ned'
both Celtic in DNA attitude and look (weedy, pale and they tend to smell)the scally is here for the time being so we all better get used to it - and that means buying a decent house alarm.
