from
The Collaborative International Dictionary of English v.0.48
Roach \Roach\, n. [OE. rroche; cf. AS. reohha, D. rog, roch, G.
roche, LG. ruche, Dan. rokke ray, Sw. rocka, and E. ray a
fish.]
1. (Zool.)
(a) A European fresh-water fish of the Carp family
({Leuciscus rutilus}). It is silver-white, with a
greenish back.
(b) An American chub ({Semotilus bullaris}); the fallfish.
(c) The redfin, or shiner.
[1913 Webster]
2. (Naut.) A convex curve or arch cut in the edge of a sail
to prevent chafing, or to secure a better fit.
[1913 Webster]
{As sound as a roach} [roach perhaps being a corruption of a
F. roche a rock], perfectly sound.
[1913 Webster]