in cahoots working or conspiring together, often dishonestly; in collusion. informal

☞ In cahoots is recorded in the early 19th century, in the south and west of the USA, in the sense of 'partnership'. The origin of cahoot is uncertain; it may come either from the French word cahute meaning 'a hut' or from cohort.

2018Linwood BarclayA Noise Downstairs If Bill and Charlotte had been in cahoots-boy, there was a word she hadn't thought of in years-then some of the responsibility would have been lifted from her shoulders.