Out of kilter
Out of order; in poor health or spirits.
'Out of kilter' is an easy enough phrase to understand - so long as we know what 'kilter' means. I have to admit that, when coming to research the origin of this phrase, I didn't. I had a vague notion that it had something to do with balance or 'squareness'. As it turns out 'kilter' is a variant of an older English dialect word 'kelter', which means 'good health; good condition', so I wasn't a million miles away with my surmise.
'Kelter' hadn't quite been supplanted by 'kilter' when the 'out of...' phrase first appeared in print and the earliest examples, which are mostly from the USA, where the phrase is still more commonplace than elsewhere, are of 'out of kelter'.
In 1643, the English Protestant theologian Roger Williams travelled to America and made a study of Native American languages, especially Narragansett, an Algonquian language. He subsequently published A Key Into the Language of America, which was a glossary of the language he had heard, which included this comment:
Their Gunnes they [native Americans] often sell many a score to the English, when they are a little out of frame or Kelter.
Williams lay claim to being the first writer to document the changes to English that occurred in America - what was later the source of the George Bernard Shaw quotation that Britain and the USA were "two nations divided by a common language".
See also: out of sorts.