Worth your salt - Idioms by The Free Dictionary
worth your salt
worth your salt good or competent at the job or profession specified.
2000 Saga Magazine Every place setting is measured with a ruler because no butler worth his salt wants to get to the end of a table with say, four settings left, and nowhere to put them.
ˌworth your/its ˈsalt deserving respect, especially because you do your job well: Any teacher worth his salt knows that students who enjoy a lesson learn the most.This may refer to the fact that in Roman times soldiers were given an allowance of salt as part of their pay. The Latin word salarium (= the money given to Roman soldiers to buy salt) is the origin of the word ‘salary’.