Step on a Crack, Break Your Mother's Back
"The childhood superstition and sidewalk game that stepping on a pavement crack will bring your mother harm."
The familiar rhyme has a considerably darker documented ancestor. In the late 19th and early 20th century United States, an earlier version of this superstition circulated with explicitly racist wording, warning white children that stepping on a crack, or a line, would somehow result in a Black child or a mixed-race marriage, a product of the deep racial prejudice of the period. Over the 20th century, as that context faded from common memory, the rhyme was reworked into the racially neutral "break your mother's back" version now used purely as a children's sidewalk game, with little awareness among most people using it today of where it came from.