He was 6 when the family resettled on Chicago’s South Side. He described his youth as one of school, church, trouble with street toughs and playing the violin for both band and orchestra, under the tutelage of O. W. Frederick, a prominent music teacher at the Ebenezer Baptist Church, where Gussie McDaniel taught Sunday school. Ellas studied classical violin from 7 to 15 and started on guitar at 12, when a family member gave him an acoustic model.

He then enrolled at Foster Vocational School, where he built a guitar as well as a violin and an upright bass. But he dropped out before graduating. Instead, with guitar in hand, he began performing in a duo with his friend Roosevelt Jackson, who played the washtub bass. The group became a trio when they added another guitarist, Jody Williams, then a quartet when they added a harmonica player, Billy Boy Arnold.

The band, first called the Hipsters and then the Langley Avenue Jive Cats, started playing at the Maxwell Street open-air market. They were sometimes joined by another friend, Samuel Daniel, known as Sandman because of the shuffling rhythms he made with his feet on a wooden board sprinkled with sand.

Mr. Diddley could not make a living playing with the Jive Cats in the early days, so he found jobs where he could: at a grocery store, a picture-frame factory, a blacktop company. He worked as an elevator operator and a meat packer. He also started boxing, hoping to turn professional.

In 1954 Mr. Diddley made a demonstration recording with his band, which now included Jerome Green on maracas. Phil and Leonard Chess of Chess Records liked the demo, especially Mr. Diddley’s tremolo on the guitar, a sound that seemed to slosh around like water. They saw it as a promising novelty and encouraged the group to return.

By Billy Boy Arnold’s account, the next day, as the band and the men who were soon to be their producers were setting up for a rehearsal, they were idly casting about for a stage name for Ellas McDaniel when Mr. Arnold thought of Bo Diddley. The name described a “bow-legged guy, a comical-looking guy,” Mr. Arnold said, as quoted by Mr. White in his 1995 biography, “Bo Diddley: Living Legend.”