How to Eat Bread, 1567

Stadtbibliothek Nürnberg, Amb. 317b 2, f. 85r (1607)

Nobles, who are bilious by nature, have both crusts removed from the bread, both the upper and lower crust. And the preeminent leaders of the church and more fastidious gourmands do likewise. So you should choose the inner part of the bread, because it provides better, more substantial, and faster nourishment than the crust. For people who are healthy but have a humid stomach, or people who want to lose weight, it is sometimes permissible to eat crusts after other foods. 

Johann Curio, De conservanda bona valetudine 

Just as you suspected: your crust-rejecting toddler is actually a bilious Renaissance lord.