Q From Glenn Morton, London: Somebody here at work just remarked ‘By Joe’. I said ‘Don’t you mean By Jove?’ ‘I don’t know,’ he replied, ‘everybody I know says By Joe. What does By Jove mean anyway?’ ‘I haven’t a clue,’ says I, ‘but I know a man who might.’
A Your belief in my abilities is both gratifying and slightly alarming. In this case, though, your trust is not misplaced. Jove is the older name the Romans had for the god Jupiter (which derives from an alteration of Jovis pater, father Jove). Jupiter was the Roman god of the sky, the sovereign deity who had powers over both gods and men (he was later identified with the Greek Zeus). If you got on his wrong side, he started chucking thunderbolts at you. There was a temple to him on the Capitol in Rome.
From medieval times, Jove has been used in English as a poetical way of referring to Jupiter. It has also been linked to Jehovah, a form of the Hebrew name of God used in some translations of the Bible. By Jove was a mild oath, an exclamation that indicated surprise or gave emphasis to some comment, which dates from the sixteenth century. It was originally a neat way of calling on a higher power without using the blasphemous by God. Shakespeare used it in Love’s Labours Lost in 1588: “By Jove, I always took three threes for nine”.
It’s a very British expression (as indeed is your haven’t a clue and your reference to I know a man who can, a current advertising slogan from the Automobile Association). It’s usually associated with bluff and hearty males from the nineteenth and early twentieth century, which seems to have been its heyday. As in J M Barrie’s The Admirable Crichton: “By Jove! I say, John, what an observant beggar he is”. I really thought it had vanished from the world of words, though a quick look around shows quite a number of examples. However, these mostly seem to be used jokingly, or in reference to earlier times.
By Joe is a wonderful variation, only possible in a period in which knowledge of classical matters is all but extinct. But then, as Ogden Nash said, anyone can make a mistake:
Even Jupiter, ruler of gods and men;
All the time he was going around with Io,
he pronounced it Ten.