The conjunction ergo is similar in meaning to therefore and hence. Although it is widely regarded as archaic, it is not as rare as some archaisms. It appears especially often in recent sportswriting, a trend we can’t explain.
Also see our article on therefore vs therefor.
Here are two examples of ergo in older texts:
This priest-book par excellence opens, as is fitting, with the great inner difficulty of the priest: he faces only one great danger; ergo, “God” faces only one great danger. [H.L. Mencken, translation (1923) of The Antichrist by Nietzsche]
If ever he attempted to show the non-existence of Deity, his negation was solely directed against the gross human notions of a creative power, and ergo a succession of finite creative powers ad infinitum … [Charles Southeran, Percy Pysshe Shelley as a Philosopher and Reformer (1876)]
Today, the word is almost always used ironically or to create a lighthearted tone, and it’s harmless—for example:
Then, more recently, the news that one in four lap-dancers have degrees was greeted in some quarters with suggestions that lap-dancing was, ergo, a perfectly respectable career choice for intelligent young ladies. [The Guardian]
To the O.S.H.B.’s, Zinn hated injustice in America; ergo, he hated America; ergo, he was a Communist. [The Villager]