GARBLING, TO GARBLE –
Garbling is the old-fashioned and technical term used by herbalists to denote the process of stripping dried herb leaves from their stems, removing the ‘impurities’ such as twigs and stems, yellowed and decayed leaves, fauna, etc. to prepare them for storage and/or use.
The word garble has been around for a while—500 years in English and more in other languages. It was first applied not to communications but to trade goods. It was used to describe sorting the good from the bad. For example, picking the husks out of a shipment of spices was called ‘garbling‘.
The Oxford English Dictionary tells us that it had different forms within Arabic and that this likely means it wasn’t originally from Arabic. Instead, it might be related to the Latin word for “sieve.”
This meaning was used in English also to apply to people, so that if you were going to decide on membership in a club you would ‘garble’ the applicants so that you would accept your favorites, but not allow people you didn’t like.
The word changed its meaning in English. Originally sorting good from bad, it soon came to mean mixing bad in to fake more of the good. In other words, traders were evidently trying to pad their shipments. This intentional contamination of commodities was what lead to the word being used to mean intentionally misrepresenting messages. From there a logical progression would seem to be that unclear messages were called by the same term, garbled, even when the loss of message clarity was unintentional.
Origin of GARBLE
Middle English garbelen, from Old Italian garbellare to sift, from Arabic gharbala, from Late Latin cribellare, from cribellum sieve; akin to Latin cernere to sift. First Known Use: 15th century
Sheepy Hollow Farm 
