Definition of "boyish"

He did so, but very soon stopt again to say, “the piano-forte! Ah! That was the act of a very, very young man, one too young to consider whether the inconvenience of it might not very much exceed the pleasure. A boyish scheme, indeed!—I cannot comprehend a man’s wishing to give a woman any proof of affection which he knows she would rather dispense with; and he did know that she would have prevented the instrument’s coming if she could.”

1815 December (indicated as 1816), [Jane Austen], chapter XV, in Emma: […], volume III, London: […] [Charles Roworth and James Moyes] for John Murray, pages 279–280

He is never expected to act like a nice little gentleman, for he is only a rude little slave. Thus, freed from all restraint, the slave-boy can be, in his life and conduct, a genuine boy, doing whatever his boyish nature suggests; […]

1855, Frederick Douglass, “The Author’s Childhood”, in My Bondage and My Freedom. […], New York, Auburn, N.Y.: Miller, Orton & Mulligan […], part I (Life as a Slave), page 41