The term 'Chunk of History' can be broken down into two crossword solutions: ERA (3 letters). An ERA is a period of time in history that is defined by certain characteristics or events. It is usually used to refer to a long period of time, such as the Stone Age or the Renaissance. It can also refer to a shorter period of time, such as the Cold War or the Industrial Revolution. In either case, an ERA is a distinct period of time that is marked by certain events or characteristics.