The first generation of editors of the Oxford English Dictionary were especially literate men and this shows in their definitions, which sometimes needed a dictionary to interpret them (luckily, the reader always has one immediately to hand, if rather cumbersome).
Take wanion. Its still-current OED definition, written nearly a century ago, says: “An altered form of ‘waniand’ used in certain formulas of asseveration or imprecation.” A modern dictionary aiming at plain English definitions might say instead that in set phrases it meant an emphatic statement or curse.
In itself, wanion means “in the waning of the moon”. It’s from the Old English verb wanian, to lessen, from which we get wane. You may feel wanion is too mild and agreeable a word to be attached to a curse, but in bygone centuries the waning of the moon was thought to be an unlucky time. Various fixed expressions took on the word and the idea, such as with a (wild) wanion (with a plague or with a vengeance), a wanion on (a curse on) and fetch one a wanion (bring one a misfortune).
Up, with a wild wanion! how long wilt thou lie?
Up, I say, up, at once! up, up, let us go hence:
It is time we were in the forest an hour since.
The History of Jacob and Esau, 1557, probably written as a school play by an unknown headmaster for his pupils to perform.
Look how thou stirrest now! come away, or I’ll fetch thee with a wanion.
Pericles, by William Shakespeare and George Wilkins, 1608.
By the early nineteenth century the phrases were old-fashioned, if not archaic. They were resurrected by Sir Walter Scott, who loved such expressions and single-handedly made a number of them familiar to his readers in his historical romances, if not going so far as to return them into daily use.
But, as he pressed upon her with a violence, of which the object could not be mistaken, and endeavoured to secure her right hand, she exclaimed, “Take it then, with a wanion to you!” — and struck him an almost stunning blow on the face, with the pebble which she held ready for such an extremity.
Woodstock, by Sir Walter Scott, 1855.
Our views of the moon today are coloured by romantic ideas of love or unrequited yearnings and we see no harm in its phases, whether waxing or waning.