The word 'salary' comes from salt payments in ancient Rome

The Latin word 'salarium' — from which English derives 'salary' — is linked to 'sal' (salt). The exact mechanism is debated: some ancient sources claim Roman soldiers were paid in salt or given an allowance to buy it; others suggest the connection is more metaphorical, salt being associated with worth and trade. Whether or not soldiers were literally paid in salt, the association was strong enough that the phrase 'worth his salt' entered English as an idiom for competence, and the word salary retains the mineral in its etymology two millennia later.

Source: Ayto, Word Origins: The Hidden Histories of English Words (2005)