salt" is used in some crypto algorithms. It is a "random" string you prefix to something to avoid to have the same cyphertext for the same clear text. Maybe an example makes it clearer. On UNIX servers they used to encrypt the password in the /etc/file. Lets imagine some crypto function that encrypts the password "mypassword" to "aC&@@uP23y". On these UNIX systems anyone could read the /etc/passwd file. Imagine I see someones encrypted password and it is exactly the same as my encrypted password (in the same file). I now know the other user has the same password as me (unlikely, but it could happen). In order to prevent this a "salt" is added (prefixed to the cleartext password) If I recall correctly, the salt originally used was the username. Instead of encrypting "mypassword" they would encrypt "usernamemypassword" and store this result in /etc/passwd. Since usernames are always different if two users would by accident have the same password, the /etc/passwd file would not reveal this...
It's not a "grain of salt", but at least "Salt" in the context of crypto...
CU
G.