Led Zeppelin IV, the band’s fourth album appeared with no official name and very little information about its contents. Instead, there were four symbols placed on the cover. Each of these were selected by one of the band mates and have grown to become symbolic of the band as a whole. Each member selected their symbol for a different reason:
Robert Plant's symbol is a circle around a feather, which is meant to symbolize his talents as a writer while also alluding to Ma’at, an Egyptian goddess of justice and fairness who is often represented by a feather.
Jimmy Page designed his symbol to spell “ZOSO.” He’s never publicly stated what the symbol means, but it is known that unlike several of the other members, Page designed this symbol himself and did not select it from another source.
John Paul's symbol is a circle placed over three interlocking ovals, which he discovered in Rudolf Koch's The Book of Signs. It represents the Christian Trintiy and was thought to serve as a symbol of protection during exorcisms.
John Bonham's symbol was also discovered in The Book of Signs. It’s said that he selected the sign simply because he liked the way it looked, though it’s technically also a symbolic represntation of the Christian Trinity.