National Janice Day

The birth record answers quickly, and then goes quiet. Janice's share of American baby girls roughly doubled in 1900. It then sat on a plateau for six years, never passing 51 girls in a single year.

Ford did not see what came next. A disinherited brother shot him in 1902. He was 37, and the reference entry places the killing at the height of his powers.

None of this explains the name's real ascent. Janice climbed through the 1930s and 1940s and crested in the middle of the century, decades after the last of these events. Whatever carried it that far arrived long after the book.

The day itself is the opposite case. Its beginnings are undocumented, and the Federal Register holds nothing under the name. It seems to have spread by circulation rather than by decree.