Signed Languages are different. It's hard for people who don't talk a Signed Language to understand because of the Blub Paradox. The word "Blub Paradox" in its

Signed Languages are different. It's hard for people who don't talk a Signed Language to understand because of the Blub Paradox. The word "Blub Paradox" in itself is a good example of what Deaf people do if they encounter concepts they need to communicate. They make up words. Signed Languages are very productive in making up words. So it is not just an idiom, slang or jargon, it is more than that.