Origin
The French idiom “filer un mauvais coton” emerged in 18th-century France among weavers. When the fabric was of poor quality or too worn, it was known to start throwing cotton.
The phrase itself literally translates as “to spin a bad cotton.” It is more appropriately translated as “to spin a bad thread.”
It is very rare for word-for-word translations to hold the appropriate nuance of an expression.
English Equivalents
The idiom “filer un mauvais coton” specifically denotes being in a situation where troubles keep accumulating, following one after another.
In English, there are three approximate equivalents:
“to be going downhill”
“to be in a bad way”
and/or
“to go down a bad path”
Note that the idiom holds the nuance of “being on the wrong track,” which has a slightly different nuance in English than “going down a bad path,” though they are somewhat interchangeable in English (depending on context).
Usage
Les trois derniers films de ce réalisateur ont reçu un accueil mitigé, et même chez ses plus fervents admirateurs, on dit qu’il file un mauvais coton.
The last three films of this director received mixed reviews, and even his most ardent admirers say that he’s going downhill.
Vocabulary
filer: a transitive verb meaning “to spin”
mauvais: adjective/adverb meaning “bad”
un: article for a masculine noun meaning “a” (i.e. one of that noun)
le coton: masculine noun meaning “cotton”
Sources
Régina Maire. 500 Expressions Françaises. Delhi India: ESI Publications, 2014, p.149.
“Filer un mauvais coton.” In Merriam-Webster’s Easy Learning French Idioms. Springfield, Massachusetts: HarperCollins, 2011, p.12.
A Writing Vice 