From The Collaborative International Dictionary of English v.0.48:
Crusty \Crust"y\ (-[y^]), a.
1. Having the nature of crust; pertaining to a hard covering;
as, a crusty coat; a crusty surface or substance.
[1913 Webster]
2. [Possibly a corruption of cursty. Cf. Curst,
Curstness.] Having a hard exterior, or a short, rough
manner, though kind at heart; snappish; peevish; surly.
[1913 Webster]
Thou crusty batch of nature, what's the news?
--Shak.
[1913 Webster]