Since the kidnapping of 276 schoolgirls in Nigeria last month, the meaning of Boko Haram—the name used by the terrorist group that seized the girls—has become more widely known. The translation from the Hausa language is usually given in English-language media as "Western Education Is Forbidden," though "Non-Muslim Teaching Is Forbidden" might be more accurate.

But little attention has been paid to the group's formal Arabic name: Jam'at Ahl as-Sunnah lid-da'wa wal-Jihad. That roughly translates as "The Fellowship of the People of the Tradition for Preaching and Holy War." That's a lot less catchy than Boko Haram but significantly more revealing about the group and its mission. Far from being an aberration among Islamist terror groups, as some observers suggest, Boko Haram in its goals and methods is in fact all too representative.

The kidnapping of the schoolgirls throws into bold relief a central part of what the jihadists are about: the oppression of women. Boko Haram sincerely believes that girls are better off enslaved than educated. The terrorists' mission is no different from that of the Taliban assassin who shot and nearly killed 15-year-old Pakistani Malala Yousafzai—as she rode a school bus home in 2012—because she advocated girls' education. As I know from experience, nothing is more anathema to the jihadists than equal and educated women.

How to explain this phenomenon to baffled Westerners, who these days seem more eager to smear the critics of jihadism as "Islamophobes" than to stand up for women's most basic rights? Where are the Muslim college-student organizations denouncing Boko Haram? Where is the outrage during Friday prayers? These girls' lives deserve more than a Twitter hashtag protest.

Organizations like Boko Haram do not arise in isolation. The men who establish Islamist groups, whether in Africa (Nigeria, Somalia, Mali), Southwest Asia (Afghanistan, Pakistan), or even Europe (U.K., Spain and the Netherlands), are members of long-established Muslim communities, most of whose members are happy to lead peaceful lives. To understand why the jihadists are flourishing, you need to understand the dynamics within those communities.