Where does the phrase “to eat a person’s salt” come from and What does it mean?

The phrase “to eat a person’s salt” means: To be on terms of amity.

From time immemorial the sharing of salt with another has been a sign of hospitality and, therefore, a token of friendship.

Among the ancient Greeks, the oath taken “with salt and over the table” was held as an expression of sacred hospitality.

The Arabs say, “there is salt between us.”

And, in the Revised Standard Version of the Bible, we read in Ezra, Chapter iv, how the enemies of the Hebrews went to the king and, in token of friendship, said to him, “Now because we eat the salt of the palace and it is not fitting for us to witness the king’s dishonor . . . We make known to the king that, if this city [Jerusalem] is rebuilt and its walls finished, you will then have no possession in the province Beyond the River”, because it was certain that the Jews would rebel and pay no tribute.