The roots of 1. FC Köln can be traced back to the year 1948, when several sports clubs in Cologne decided to merge amidst the post-war reorganization of German football by occupying Allied forces (source). The founders envisioned a united club that would represent the city on a national level, giving birth to its now-familiar moniker – "Effzeh", short for 'FC' spoken in local dialect.
Despite humble beginnings, 1. FC Köln wasted no time establishing themselves as a force in German football. In their maiden season (1949-1950), they finished second behind Borussia Mönchengladbach in Oberliga West, arguably Germany's toughest regional league at that time.
However, it was not until the formation of Bundesliga in 1963 did Effzeh truly started making waves nationally (source). With legendary coach Hennes Weisweiler at helm and star players like Hans Schäfer leading from front, they won inaugural Bundesliga title - cementing their place amongst German soccer elite.