No one is exactly sure who first coined the New Firm label that accompanied the emergence of Aberdeen and Dundee United as serial contenders for the trophy in the late 1970s and early 1980s.
The nickname was in common use across the media before its combined impact on the Scottish football landscape reached its zenith in 1983, when United became national champions for the first time and the Dons lifted the European Cup Winners' Cup in Gothenburg.
This season will mark the 40th anniversary of the last time a team other than Celtic or Rangers became Scottish champions and since then the New Firm brand has inevitably lost much of its resonance.
However, this afternoon's encounter between United and Aberdeen at Tannadice at least has some faint echoes of a time when club rivalry was arguably the most compelling in the country.
Dundee United's Sam Dalby battles with Aberdeen defender Gavin Molloy
Jimmy Thelin has had a great start to life as Dons boss but his team has stagnated of late.
Jim Goodwin's team is flying high in fourth place after winning promotion last season
Jim Goodwin and Jimmy Thelin can operate with more modest ambitions and against a backdrop of reduced expectations compared to those that underpinned the brilliance of Jim McLean and Alex Ferguson in their respective roles four decades ago.
However, in their own way, United manager Goodwin and his Dons counterpart Thelin have engineered a situation that has given the match a new sense of importance.
Victory for Goodwin's side would take them just three points behind third-placed Aberdeen, who are desperately trying to halt a seven-game winless streak that has taken some of the shine off Thelin's remarkable start to life on the bench. Pittodrie.
Striving to be the best of the rest behind the Old Firm is now the loftiest goal either club can realistically pursue. The heady days his supporters enjoyed under McLean and Ferguson are simply unattainable now.
The financial playing field back then was almost as level as the one on which those managerial titans regularly gave Celtic and Rangers bloody noses. Wages paid by the Glasgow giants were at a similar level to those of the New Firm, while the then-restrictive nature of player contracts largely allowed McLean and Ferguson to prevent their best players from moving elsewhere.
In nine of the 14 seasons from 1978 to 1991, which began with Ferguson replacing Billy McNeill as Aberdeen manager and ended with the redoubtable Alex Smith in charge, the Dons won the title three times and were runners-up on six occasions.
During the same period, all under McLean's strong rule, United won that historic first title in 1983 and finished third six times.
Aberdeen's back-to-back titles in 1984 and 1985 meant that Scottish football had gone three consecutive seasons without either Celtic or Rangers becoming champions for the first time. Since then, Old Firm hegemony has never been breached.
United striker Sam Dalby is the Premiership's top scorer with nine goals
In the early months of this season, Aberdeen fans dared to dream that Thelin could be the man who could change all that.
The soft-spoken, poker-faced Swedish manager arrived at a club in some disarray, having finished in the bottom six of the Premiership in two of the previous three seasons.
While Thelin had a reputation as one of his country's most respected managerial talents, no one could have anticipated the immediate impact he would have at Pittodrie.
Including an impressive 13-game winning streak since the opening day of the season, Thelin guided Aberdeen to 16 wins in his first 18 games in charge in the League Cup and Premiership.
His first bump in the road barely deserved that description: his team came back from 2-0 down to draw 2-2 at Celtic Park in October to stay on terms with the reigning champions at the top of the table and further fuel the conversation. excited about their credibility as title challengers.
However, Aberdeen's next trip to Glasgow proved to be a thoroughly trying experience as a fired-up Celtic asserted their authority and underlined their current superiority with a 6-0 victory in the League Cup semi-final at Hampden.
Apart from the 4-1 home win over Dundee in their next match, Aberdeen have subsequently suffered a marked drop in form. They have lost four and drawn three of their last seven outings and the drop in performance levels hit a new low on Boxing Day when they were beaten 4-0 by Kilmarnock at Rugby Park.
Just as Thelin studiously avoided making grandiose predictions about his team during its winning streak, he has resisted being too pessimistic in his assessments of its current struggles.
Jim McLean led Dundee United to the Premier Division title in 1983.
Sir Alex Ferguson and his assistant Archie Knox lift the European Cup Winners' Cup for Aberdeen in 1983
The 46-year-old can expect strong support from club president Dave Cormack in the upcoming transfer window to continue revamping his first-team squad as part of what both parties consider a longer-term project.
That said, while Thelin has plenty of credit in the bank with a revitalized Aberdeen fan base, he will be wary of the need to get back to winning ways as quickly as possible. As far as those supporters are concerned, there would be no better place to start than Tannadice, as the New Firm rivalry has remained as intense as ever off the field, even as standards have lowered on it.
United, whose last third-place finish in the top flight was in 2010 under Peter Houston in a season in which they also won the Scottish Cup, go into the contest as slight favorites after an encouraging recent run in which they lost just one game. of his last eight games.
Tannadice is proving to be the scene of managerial redemption for Goodwin, who was on the wrong side of the equation the last time United beat Aberdeen there in October 2022.
The 4-0 thrashing was a preview of the trauma Goodwin would suffer during his time in charge of Aberdeen and which ultimately saw him sacked the following January following an ignominious Scottish Cup exit at Darvel and a 6-0 humiliation to the Hibs at Easter. Path.
Dundee United surprised by offering Goodwin a swift return to work just two months later, but although he was initially unable to save them from relegation, his appointment was later vindicated.
The Irishman won them back at the first attempt with a Championship title win last season and they have done more than decently so far in their return to the top flight.
Goodwin is undoubtedly repairing a reputation as a manager, forged by his impressive work at Alloa Athletic and St Mirren, which was badly damaged by his painful experience at Aberdeen.
United's player recruitment during his tenure has proven shrewd with acquisitions such as Jack Walton, Will Ferry and David Babunski helping to revitalize a team that, like Aberdeen under Thelin, has notably reconnected with a support that had previously suffered. for a long time.
With Hibs and Hearts battling it out in the bottom six of the Premiership for most of this season, the way has been cleared for Aberdeen and Dundee United to once again become a combined presence in the wake of the Old Firm.
Tonight's showdown could prove pivotal in indicating which of them is best equipped to stay the course over the next five months.
Forty years on, the title may be out of reach, but the New Firm are still capable of offering their own brand of intrigue to Scottish football.