EMV stands for "Europay, Mastercard, and Visa". When the card networks developed and implemented EMV chips as a new fraud protection technology, they changed certain policies to induce merchants to upgrade to card readers that were compatible with EMV chips. The main policy change was to make it so that merchants without EMV-compatible payment terminals would be liable for the cost of any fraud claims stemming from transactions made with non-EMV terminals. Normally, that liability would lie with the issuer, hence the “EMV liability shift” from issuer (cardholder's bank) to acquirer (merchant’s bank). Certain reason codes relate to this liability shift.
