The article focuses on the development of terms which were used in antiquity and Middle Age Europe to denote public opinion (fama, existimatio, opinio in Ancient Rome, fama publica, communis opinio in the Middle Ages etc.). Particular attention is paid to the distinction made in Roman public life between a fama, which represented common opinion, and a rumor, which meant undervalued and unreliable opinion of the plebs. The medieval term fama, more often fama publica, referred to a local information network or mechanism of collective evaluation of individuals' esteem. It was also an important part of court proceedings. Both historic eras were concerned with rumor in today's sense of the word, which often comprised or underlaid common opinion.