Today being Halloween, I am going to look in this post at words and expressions in English that are linked in some way with witches, even though that is not always apparent when we use them these days.
fly-by-night: nowadays usually means unreliable when talking about companies or businesspeople, but the first citation in the OED is from Grose's A Classical Dictionary of the Vulgar Tongue (1796), whose definition is "an ancient term of reproach to an old woman, signifying that she was a witch".
weird: Shakespeare referred to the three witches in Macbeth as the 'Weird Sisters', and there is an entry in the OED, weird-woman, defined as 'a witch'. Weird has its origins in the Old English wyrd, which meant fate or destiny. The plural form referred to the Fates, the three goddesses believed to determine the course of human life.
hag: this word, according to the OED is "usually conjectured to be a shortened form of Old English hægtesse, hæhtisse, hægtes, -tis, hegtes ‘fury, witch, hag’", although the Dictionary says that, even though the meaning would suggest a link, the form-history is not clear. The first definition given in the OED is 'An evil spirit, demon or infernal being in female form', and another definition is 'A woman supposed to have dealings with Satan and the infernal world; a witch'.
sink or swim: the OED says that this idiom is particularly associated with the practice of throwing a suspected witch into the water to see if she sank (meant she was innocent) or stayed afloat (in which case she was considered to be a witch). One definition of the verb swim, in a transitive form, given in the OED, is 'To put (a person suspected of witchcraft) to the ordeal of being immersed in water, the proof of innocence being that the person did not sink', for instance, as in the 1748 citation 'Alice, the wife of Thomas Green, labourer, was swam, malicious..people having raised an ill report of her for being a witch.'
fascinate: the earliest sense (early 17th century) of this word, according to the OED, was "to affect by witchcraft or magic; to bewitch". The meaning only became dissociated from witchcraft two centuries later.
witches' knickers: Irish slang for discarded plastic carrier bags that get caught in trees and bushes. This was probably a more common phenomenon several years ago before supermarkets started charging for carrier bags (which they did earlier in Ireland than in Britain).