As police continue to assess reported threats to Catholic schools from the Red Hand Defenders, it is understood the codeword used in weekend calls to newsrooms dates back more than a decade.
The PSNI responded to the threat by putting neighbourhood officers on the ground yesterday, with other back-up resources available.
A senior officer told this newspaper: "We didn't see any activity today [Monday] to give us any concern."
There is an assessment that the mainstream loyalist paramilitary organisations – the UVF and UDA – are not involved and are opposed to any threat or protest activity at the schools.
The codeword used in weekend calls to newsrooms was first used more than a decade ago and is widely known.
As police continue to investigate, Secretary of State Theresa Villiers yesterday condemned what she called "the shocking threats to Catholic primary schools in north Belfast".
For years coded telephone calls have been used by loyalists and republicans to deliver statements and threats and so-called 'claims of responsibility'.
The codeword is meant to authenticate the communication.
It sounds simple, but it isn't.
At times the calls can be bogus – information delivered often anonymously and on occasions using labels and titles to hide something or someone else.
The Red Hand Defenders is one such example; a name that emerged long after the ceasefires of 1994.
It was the label used by loyalists in 1999 and 2002 to admit the killings of solicitor Rosemary Nelson and postman Danny McColgan – murders carried out by the LVF and UDA.
In 2001, one of the UDA's most senior leaders on the Shankill used the cover name of Red Hand Defenders to make a bomb warning – a call that a device had been left at the Holy Cross Girls Primary School in north Belfast.
It turned out to be a hoax.
And, in January 2002, the UDA staged a farcical news conference in a drinking club using masked men to deliver a warning that the Red Hand Defenders had 14 days to stand down.
I was at that news conference and in interviews at the time said the UDA could achieve this by talking to itself in the mirror – its members repeating, 'I must not be a Red Hand Defender'.
Loyalists were fooling no-one but themselves.
In periods of internal feuding, the title was also used by loyalists to threaten other loyalists, including those at the top of the UDA, UVF and Red Hand Commando.
This is the background context and confusion that has to be understood in assessing this latest threat.
It may have been made to further raise tension in an already volatile climate in north Belfast.
The police say they will continue to monitor the situation.
We won't be intimidated, vow defiant parents
Anxious parents of children attending one of three Catholic schools under loyalist threat have said they won't be intimidated.
It follows an alleged threat from the Red Hand Defenders, in which a man claimed that parents, pupils and teachers were not welcome at schools in "Protestant, unionist and loyalist areas".
He said that "military action" would begin if the threat against Holy Cross Primary, Mercy Primary and Mercy College schools, was not taken seriously.
But yesterday, parents defied any threat to ensure their children attended classes.
From a distance it looked like a normal Monday morning school run as excited children bounced out of cars, giving mums and dads kisses goodbye before racing in to school laughing with their friends.
They seemed blissfully unaware of any potential dangers.
But after the children disappeared through the doors of Holy Cross Primary, their parents told of their unease.
Sinead McGibbon (37) said: "These are my children and this is their education. It's the year 2013, so why is this being taken out on my kids? Why should I bow down to them?
"My husband wasn't too fussed on bringing them to school today, but I just asked him, 'Why?'
"It's so unfair – on the principal, the parents, the pupils."
A 41-year-old mother who did not wish to be named, said she had spent the early hours wondering what to do.
"The first time I heard about it, I felt sick with nerves but the stress hit me last night, and I couldn't sleep. We've seen it before and I thought we were away from all this," she said.
"I have been up since 5am trying to decide whether I should bring her to school or not, but she is completely unaware and skipped in to school this morning – she knew nothing."
She continued: "All the parents are feeling the same, everyone has been texting each other.
"It is so frustrating because it is just a minority who want this. The rest don't want any of this."
After waving goodbye to his daughter as she set off on her first day at the school, one father who did not wish to be named said it was just "scaremongering."
A low-key police presence was a subtle reminder of the potential trouble. A police Land Rover patrolled past a yellow bus full of smiling children on their way to school, while officers sat in an unmarked police car near Mercy Primary.
A 48-year-old father said that targeting children was a "disgrace". "At the end of the day, it's just children. Kids shouldn't be aware of any of this going on," he said.
The threat has been met with widespread condemnation, including by the UDA and UVF.