From Longman Dictionary of Contemporary Englishsomebody’s lord and mastersomebody’s lord and masterOBEYsomeone who must be obeyed because they have power over you – used humorously → lord
Examples from the Corpus
somebody’s lord and master• Could he bear to see them wired-made vulnerable to the least whim of their lords and masters?• In the rustic humour there were opportunities for poking fun at lords and masters and oppressive authority, both civil and military.• Meanwhile our lord and master would sit and drink one cup of tea after another, barking orders from time to time. 