the.com/terrible twos

means The developmental stage, roughly around age two, when toddlers assert independence through tantrums, defiance, and relentless boundary-testing.

from A 20th-century American parenting phrase — not formal science but kitchen-table folklore, coined to describe the explosive gap between a toddler's surging willpower and their still-tiny vocabulary for expressing it. 'Terrible' here isn't moral judgment, it's exhausted affection; the phrase spread through parenting books and playground chatter until it became the default name for the age, even though pediatricians note the behavior often starts before two and lingers well past it.