I learned 冗談 (jou-dan = useless-talk) as a word for "joke", but I was curious about other uses of 冗.
I ran across 冗句 (jou-ku = useless-phrase) as another word for joke and it made me laugh...
Wiktionary calls it a "phono-semantic matching", meaning that it manages to be compatible in both sound and meaning with English "joke".
I think 冗句 is an uncommon usage, normally it's written as ジョック like a more standard loanword.