Metalworking Shopkeepers in Cairo Suqs Using Hebrew words in a Private Language?

Here's a wild and wonderful story if it can be borne out:  Jacky Hugy for Al-Monitor's Israel Pulse writing on "The Secret Language Of Cairo's Jewelry Merchants," quoting research by Hebrew University Professor Gabriel M. Rosenbaum on a secret language used by jewelry merchants in the Khan al-Khalili and other jewelry suqs in Egyptian cities. He thought he recognized a few Hebrew terms when they were speaking in a private patois among themselves (and he's a Professor of Arabic so he wouldn't be fooled by cognates), and claims to have traced it back to the Middle Ages, when most of the metalworkers were Karaite Jews, and apparently used Hebrew jargon as a secret language. Some of the evidence cited:

Thus, for example, in market jargon the word yaffet means "good" or "nice," similar to its meaning in modern Hebrew. The merchants use it to share information about clients who look wealthy or give their opinion of a good product. “The opposite of yaffet is ashfoor,” says Rosenbaum, “a word whose root is unknown, and which does not suggest a Hebrew parallel.”

Some of the merchants use the word zahub, whose origin is the Hebrew word zahav for gold, to refer to one Egyptian lira. When they want to hint to a colleague that he better get rid of a customer, the merchants tell him halakh, or ahalakh, which sounds like halah, the word for "go" in modern Hebrew. Others use the word admoon. It means an "old tool," or a piece of jewelry that was repaired, and that the merchant polished up and shows in his display window as if new. Its origin is in the Hebrew word kadmon, which means "ancient" or "old." In colloquial Egyptian Arabic, the Hebrew letter kof (k) is pronounced as an alef (a silent letter), and thus kadmon became the term admon among Egyptian merchants. The possessive word they use, shal, is also taken from Hebrew. Shali means "in my possession" or "with me," while shalakh means "in your possession" or "with you." But the greatest influence is in the realm of numbers. The merchants and metalsmiths in Egypt’s marketplaces actually count in Hebrew: echad (1), shnayin (2), shlosha (3), shloshin (30), shishin (60), shefin (70), shmonin (80) and so on.

It's credible enough; I know some folks in the market will use various code words, or Nubian, or in one case I heard of Swahili, to talk without their customers' understanding. I rather doubt that today's mostly Muslim and Christian shopkeepers are aware they're using Hebrew words and numbers, though.

Karaite Jews were a sect of Judaism, still found in Israel and a few pockets elsewhere, who accepted the Torah but rejected the Talmud and were once highly prominent in many Middle Eastern societies.