The 37-year-old boss left Google in July to lead a high-profile turnaround at Yahoo –the first person ever to take charge at a Fortune 500 company while pregnant.

Ever since Mayer delivered her baby on September 30, the public has known him only as BBBB—Big Baby Boy Bogue, the moniker given to him by mom and dad, Zachary Bogue.

Turns out, Mayer and husband Zack, a lawyer who recently started a fund to invest in big-data companies, considered a couple of dozen names from friends but settled on one that they had been thinking about for a while.

Why Macallister? Mayer has a thing for M’s—she’s an MM, as is her mother, Margaret. More importantly, the parents decided that Macallister Bogue has a strong Scottish ring to it.

Mayer, whom I profiled in the current 40 Under 40 issue of Fortune, sped through maternity leave and has been back at Yahoo since last Monday. Today at 5 p.m. EST, she conducts her first-ever quarterly earnings call. You can listen to the call here.