I don't know how you got this turned on accidentally, but you can remove it by entering these two lines in Terminal.app:
defaults delete com.apple.dock desktop-picture-show-debug-text
killall Dock
Why my desktop displays location path of the chosen image?
I don't know how you got this turned on accidentally, but you can remove it by entering these two lines in Terminal.app:
defaults delete com.apple.dock desktop-picture-show-debug-text
killall Dock