hanky-panky

UK: /ˌhæŋkiˈpæŋki/ US: /ˈhæŋkiˈpæŋki/ ,(hang′kē pang′kē)

WordReference Random House Learner's Dictionary of American English © 2025

han•ky-pan•ky or han•key-pan•key /ˈhæŋkiˈpæŋki/   n. [uncountable] [Informal.]

1. Informal Terms illegal or unethical behavior or dealings:
   a little financial hanky-panky.
2. Informal Terms improper sexual relations.

WordReference Random House Unabridged Dictionary of American English © 2025

han•ky-pan•ky  (hang′kē pang′kē), n. [Informal.]

1. Informal Terms unethical behavior;
   deceit:
   When the bank teller bought an expensive car and house, they suspected there might be some hanky-panky going on.
2. Informal Terms illicit sexual relations.

Also, han′key-pan′key, han′ky pank′. 

• 1835–45; rhyming compound; compare initial h, p of higgledy-piggledy, hocus-pocus, hodge-podge, etc.

Collins Concise English Dictionary © HarperCollins Publishers::

hanky-panky / ˈhæŋkɪˈpæŋkɪ/ noun

1. dubious or suspicious behaviour
2. foolish behaviour or talk
3. illicit sexual relations

Etymology: 19th Century: variant of hocus-pocus