- The term tautology is originally used in rhetoric to refer to statements that are in-themselves redundant. For example, the phrase “unsolved mystery” is a rhetorical tautology because any mystery is unsolved — the adjective is unneccessary and adds no meaning to the phrase. The same thing commonly happens with acronyms. For example, the acronym ATM means “automatic teller machine”. So, the common phrase “ATM machine” is a rhetorical tautology, as they are essentially saying “automated teller machine machine”. The same thing happens with “PDF format”, “PIN number” and “UPC code”.
This is incorrect, "atm machine" is a pleonasm, it has got nothing to do with rhetorical tautologies. RT guarantee the truth of the argument, where the expectation is for it to be falsifiable. Figure of speech and pleonasms has nothing to do with this.
http://changingminds.org/techniques/language/figures_speech/tautology.htm confuses pleonasm with tautology