Pet form of Robert, from Germanic 'hrod' (fame) and 'berht' (bright), meaning 'bright fame.'
Bob is a medieval rhyming nickname for Robert — itself a Germanic compound of hrod (fame) and beraht (bright), meaning "bright fame." The English medieval habit of creating rhyming pet names — Will from William, Hob or Bob from Robert, Dob from Dorothy — produced a whole class of names that eventually achieved independence. Bob's path from nickname to given name to cultural institution was essentially complete by the 20th century.
Few names are as thoroughly saturated with cultural presence as Bob. Bob Hope brought comedy through the depression and war. Bob Dylan redefined American music and won the Nobel Prize in Literature.
Bob Marley's voice became a global symbol of resistance and peace. In literature, the name carries a kind of deliberate plainness — Bob is the name you give an everyman, a reliable narrator, a neighbor, a saint. Charles Dickens named Bob Cratchit the overlooked clerk in A Christmas Carol precisely because the name suggested humble ordinariness that was meant to move the reader's sympathies.
By the latter 20th century, Bob had become more middle-aged than youthful as a given name, replaced in the nursery by Robert or more fashionable alternatives. But Bob's very datedness is now its charm — generational name cycles have a way of refreshing themselves, and Bob, sturdy and bright-famed as its Germanic roots promised, will almost certainly come back around.