the.com/baby boom

means A sharp, sustained spike in birth rates, especially the surge in births across the US and other countries following WWII.

from A straightforward compound of 'baby' plus 'boom' in its economic sense of a sudden upswing — the same 'boom' used for booming markets or booming industry. The phrase caught on in the postwar years as demographers and journalists watched birth rates surge and needed a quick, punchy way to describe it; 'boom' did the work of signaling explosive, almost economic-chart growth rather than gradual increase. The generation born into that surge later inherited the name itself: 'baby boomers.'