It’s a small-village-west -of-London colloquialism for being broke, for having no money.

It’s roots stem back to a rowdy game of Scrabble during my college years, it was a triple word score, and a verb described by a fellow player in a Clouseauesque accent as meaning 'to be penniless'. It's still used today, twenty five years later.
I am broke and have no money, I am ferneh.’
by Paul Gaff December 20, 2004
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