Add a new seasonal greeting to your list: Habari gani. It is Swahili for "What's new?" and the salutation for millions of African Americans who celebrate Kwanzaa, a seven-day holiday that begins on Dec. 26. Inaugurated 25 years ago as a black-nationalist celebration of familial and social values, the festivities are now being embraced by the black mainstream.
Kwanzaa is patterned after various African agricultural festivals, and the name derives from the Swahili word for first fruit of the harvest. It was created by Maulana Karenga, a black-studies professor at California State University, Long Beach. The purpose of the holiday, he...