Webster's Revised Unabridged Dictionary · 1913

Callow

Callow , adjective

[Old English calewe, calu, bald, Anglo-Saxon calu; akin to Dutch kaal, Old High German chalo, German Kuhl; compare Latin calvus.]

1.
Destitute of feathers; naked; unfledged.
An in the leafy summit, spied a nest, Which, o'er the callow young, a sparrow pressed. — Dryden
2.
Immature; boyish; “green”; as, a callow youth.
I perceive by this, thou art but a callow maid. — Old Play [1675]

Callow , noun

[Named from its note.]

(Zoology) A kind of duck. See Old squaw.