The term 'Deck Quartet' refers to four cards from a standard deck of playing cards. The four cards are Nines (5 letters), SUITS (5 letters), ACES (4 letters), and ABBA (4 letters). Nines are the ninth card in each suit, SUITS are the four categories of cards (Hearts, Diamonds, Spades, and Clubs), ACES are the highest ranking card in each suit, and ABBA is a reference to the Swedish pop group of the same name, which is also a term for a four-person group. Together, these four cards form the Deck Quartet.