domino

domino any of 28 small oblong pieces marked with 0–6 pips in each half, used to play the game of dominoes, in which each piece is laid down to form a line, each player in turn trying to find and lay down a piece with a value matched by that of a piece at either end of the line already formed. This meaning dates from the early 19th century; in an earlier sense, the word meant a loose cloak, worn with a mask for the upper part of the face at masquerades. It is originally recorded in the late 17th century, from French, denoting a hood worn by priests in winter, and is probably ultimately based on Latin dominus ‘lord, master’.
domino theory the theory that a political event in one country will cause similar events in neighbouring countries, like a falling domino causing an entire row of upended dominoes to fall (the domino effect). The term derives from a speech by President Eisenhower in 1954 on the possibility of the spread of communist rule.