I saw a poster giving various translations of the word banana. One of them was supposedly the Welsh word for banana: ffrwchnedd.
This struck me as unlikely, and indeed any decent source gives the Welsh word for banana as banana.
On the other hand, ffrwchnedd seems to exist as some kind of jocular Welsh word for banana.
It does appear in some less-than-reputable looking word lists, e.g.
It does appear in Wiktionary.
Almost all the Googlits for it relate to the discussion of the existence of this word, rather than just using it normally in an article or conversation.
But there are some exceptions.
Here’s one I found using Googlebooks: The autobiography of David R Edwards, called Atgofion Hen Wanc (2013), contains the following phrase : “lemonêd orgasmaidd ac ysgytlaeth ffrwchnedd”.
A comment on this gallery: “Wyt ti’n hoffi ysgytlaeth ffrwchnedd?”
Google translate is somewhat confounded by ffrwchnedd, as follows:
Wyt ti’n hoffi ysgytlaeth ffrwchnedd? -> Do you like aggregate anxiety?
Ffrwchnedd -> Fragments
Ffrwchnedd? -> Freshness?
sglodion a ffrwchnedd -> chips and fruit
Wiktionary does have an entry, which indicates the word is humorous.It also provides the following reference:
Iwan Wmffre, “Learners, Native Speakers and the Authenticity of Language”. In Communicating Cultures, ed. Ullrich Kockel and Máiréad Nic Craith. Münster (2004): LIT Verlag, ISBN 9783825866433, p. 162.
This work includes the following text:
… exclaim ‘They haven’t got a word for bananas!’ after he heard a conversation by Welsh native speakers. However, a term ffrwchnedd was ‘magicked’ sometime before the end of the 1980s to the satisfaction of purists, at least, and is now fairly well known, though it has not received the approval of Welsh dictionaries
So perhaps someone made up this term in the 1980s as a joke, and some people are generally aware of it but it is not really in use as a word.
Note that it bears some similarity to ffrwth (meaning fruit).