puerility

From Middle French puérilité, from Latin puerīlitās, from puerīlis (“childish, juvenile”), from puer (“boy”).

puerility (countable and uncountable, plural puerilities)

1. The state, quality, or condition of being childish or puerile.
2. That which is puerile or childish; especially, an expression which is insipid or silly.
   • Charles Kingsley

     You treat his opinions (though he never thrusts them on you) about "the Church," and his duty, and the souls of his parishioners, with civil indifference, as much ado about nothing; and his rubrical eccentricities as puerilities.

• puerilism