The three legs, like the beautiful legs of a woman, are said to symbolize the three coastlines of white, sensual, sandy beaches that run along all three coastlines (nearly 1500 miles of beaches!) Perseus, after cutting off the snaked head of Medusa, gave the head to the goddess Athena to place on her shield. In the Trinacria, just as on Athena's shield, the head of Medusa wards off any invaders, lest they be turned into stone. The three leafy flourishes intermingled with the legs represent the fertility of Sicily--stalks of wheat. At one time, Sicily was the bread basket of the Roman Empire.
Historians tell us that Spartan fighters carved a white leg bent at the knee (a symbol of strength) onto their shields. So perhaps there is also another meaning to the legs. Some say the legs are running while others say the legs are spinning.
The use of the Trinacria is much more ancient, however.... it appeared on Syracusan coins from the 4th century BC.
The Trinacria's shape is often referred to as a triskelion; this shape can be found in many places among the general Mediterranean Basin region and in many European countries like France, Sicily, Crete, Greece, the North African coast, and the Isle of Man. Celtics use a similar shape in their coins and decorative motifs. Ancient coins depicting Trinacria were found in present day Turkey. The symbol has also been found on many ancient Greek ceramics... in southern Italy and Sicily. Keep in mind that Sicily, along with Italy, was once part of ancient Greece. Some triskelions found in these locations date from as early as the eighth century BC. A modern day triskelion from the 1950s appears in that little plastic insert adapter needed to play large hole 45 rpm records on a thin spindled turntable.
Although the Trinacria appeared on coins and other archaeological artifacts in Mediterranean cultures for thousands of years, the Isle of Man has been using the symbol in an official capacity long before Sicilians.
The Normans arriving in Sicily in 1072, borrowed and modified the design of the the Trinacria and brought it back to the Isle of Man, and since 1270 used it to replace the Viking ship on their previous flag. Their similar three legs wear armor and the boots have spurs, but Medusa and the wheat are missing. The Latin motto surrounding the Trinacria on the Royal coat of arms for the Isle of Man reads, “Quocunque Jeceris Stabit”--“Whichever way you throw, it will stand”.