The Allies adopted the "V" as a symbol for VICTORY to inspire
them to fight for victory over their enemy. They printed the "V" in
advertisements and products. They held up the first two fingers in
a "V".
The Morse Code for the letter "V" is . . . - (or
Dot-Dot-Dot-Dash).
If you hum the Dot-Dot-Dot-Dash, it can begin to sound like the
first 4 notes of Bethoven's 5th Symphony.
In the movie "The Longest Day" there is a scene where this is
depicted and somewhat explained. The soldiers are on a ship at
night waiting to invade France. A plane flys over flashing a light
and spelling out "V" in Morse Code. The soldier sings the tune from
Bethoven's Symphony.