Left in the lurch
Abandoned in a difficult position without help.
This has nothing to do with lurches in the sense of sudden unsteady movements.
There are suggestions that lurch is a noun that originated from lich - the Old English word for corpse. Lych-gates are roofed churchyard entrances that adjoin many old English churches and are the appointed place for coffins to be left when waiting for the clergyman to arrive to conduct a funeral service. To be 'left in the lych/lurch' was to be in dire straits indeed.
Another theory goes that jilted brides would be 'left in the lych' when the errant bridegroom failed to appear for a wedding. Both theories are plausible but there's no evidence to support either and, despite the superficial appeal of those explanations, 'lych' and 'lurch' aren't related.
In fact, the phrase originates from the French board game of lourche or lurch, which was similar to backgammon and was last played in the 17th century (the rules having now been lost). Players suffered a lurch if they were left in a hopeless position from which they couldn't win the game. The card game of cribbage, or crib, also has a 'lurch' position which players may be left in if they don't progress half way round the peg board before the winner finishes.
The figurative usage of the phrase had certainly entered the language by the 16th century as this line from Nashe's Saffron Walden, 1596, shows:
"Whom he also procured to be equally bound with him for his new cousens apparence to the law, which he neuer did, but left both of them in the lurtch for him."
The game came to England from continental Europe and its name derives from the word 'left', which is 'lurtsch' in dialect German and 'loyrtz' in Middle Dutch. Why call a game 'left'? The most plausible explanation (and regular readers will know that, in etymology, plausibility isn't everything) is that it relates to the bad feeling against the left hand that was then commonplace in many cultures. In English we have held on to this with the word 'sinister', which of course just means 'left-handed'.