The batting order refers to the sequence in which batters come to bat after the loss of a wicket. The top three batters form the top order. The fourth to seventh placed batters make the middle order. Finally, the remainder of the batters form the “tail” and are called the “tail-enders.”
Tail-enders are players whose key attribute is bowling. Since batting is not their speciality, they are sent to bat last. It is least expected from the tail to pile up any runs. In fact, when the seventh wicket falls, a common phrase heard from the commentary box is, “the tail is exposed.”
There have been numerous instances when the total runs made by the tail is more than that of the remaining batting order. Such an unexpected occurrence is called “wag.” It is used metaphorically to denote the wagging of tail of an animal.
Historically, the seventh, eight, ninth and tenth wickets have produced century partnerships or better in both Tests and ODI cricket. The wag signifies the importance of having a proper depth in the batting order which can increase the chances of a team scoring more runs than expected.
The modern game of T20 cricket expects the tail to wag given the fast-paced nature of the sport. Thus, teams now often emphasise on ensuring that their bowlers too can come in handy as batters when needed.