A child is too old to breast-feed when he can unhook mommy's bra with one hand.

The line is a comic, deliberately exaggerated rule-of-thumb about weaning. By tying “too old” not to a medical guideline but to a culturally coded adult skill—unhooking a bra—it uses incongruity to puncture the seriousness and anxiety that often surround parenting decisions. The joke also plays on the tension between nurturing intimacy and a child’s growing autonomy: once a child can perform a coordinated, purposeful action associated with adult sexuality and clothing, the continued act of breastfeeding is framed as socially awkward. Its humor depends on taboo adjacency (child + lingerie) while ultimately commenting on shifting boundaries as children mature.