Indeed, the letter really used to be composed “uu”!
Various reports on etymological locales offer this clarification of how the change appeared to go down. In Latin, the letter “v” had an articulation near our contemporary “w” sound, however as the “v” sound changed after some time, another image must be made. Around the seventh or eighth century, copyists started to state “uu” to speak to the “w” sound. This training dropped out of support for a brief span and afterward returned after the Norman victory in 1066. After some time, the image was changed over to a “ligatured” shape, and the “uu” wound up turning into its own letter, the “w.”
The name of the 23rd letter of the English alphabet is “double u” because it was originally written that way in Anglo-Saxon times.
As the Oxford English Dictionary explains it, the ancient Roman alphabet did not have a letter “w.”
So in the 7th century, when Latin was first used in early Old English writing, it was necessary to invent a symbol to represent that sound.
At first, the sound was represented by “uu”—literally a double “u.”