Etymology: Apparently < Anglo-Norman roche (13th cent. or earlier; compare Middle French roche , roce (14th cent.)) roach, of uncertain origin; a connection is sometimes suggested with Old French (north-eastern) roque , roce , roche (13th cent.), Middle French (north-eastern) rocque ray ( < Middle Dutch roche rough n.²), although the two fishes are so dissimilar that it is difficult to see the possibility of a semantic transfer, and the form history would also present difficulties. Compare also post-classical Latin rocea (from the end of the 10th cent. in British sources), rocha , rochia , rochus (from c1180 in British sources) roach, rudd, of unknown origin (forms in -ch- are probably influenced by either Anglo-Norman or English). Given the late attestation of the word in continental sources (assuming that there is no connection with Old French roque ray), it is impossible to be certain of the relative priority and interrelationships of the words in Anglo-Norman, Latin, and English, and it is possible that the word comes from another (unidentified) source. Compare roach n.³It is uncertain whether the following early examples in Latin contexts or glossaries show the Middle English or the Anglo-Norman word:c1175 Libellus de Nominibus Naturalium Rerum in T. Hunt Teaching & Learning Lat. in 13th-cent. Eng. (1991) I. 23 Rombus vel rocea, scylga, i. roche.1314 Wardrobe Accts. Edward II 21/12 Dars, roches, et pik, 2s. 8d.1391 in L. T. Smith Exped. Prussia & Holy Land Earl Derby (1894) 53 Cuidam homini de Lettowe pro roches ab ipso emptis apud le Haff, v s. iiij d. pr. Apparently also attested early in the place name Rocheborn', Cumberland (1292; now Roachburn). The word now normally shows an unchanged plural form, although (in common with many other names of fishes) usage earlier varied between marked (with -es) and unmarked plural forms.

Etymology: Variant of roche n.¹, frequently distinguished in form in the senses below.

Etymology: Apparently a transferred use of roach n.¹ Compare earlier roach-bent adj., roach back n., roach-backed adj., roach mane n., roached adj., all apparently showing similar use.In sense 3 ultimately after roach mane n.; compare earlier roached adj. 2b.

Etymology: Shortened < cockroach n. The widespread adoption of the shortened form may perhaps have been motivated partly by embarrassing homonymy with cock n.¹ 9a (compare quot. 1837 at sense 1), and perhaps also by analogy with the word pair cockchafer n. and chafer n.¹, and with compounds of cock n.¹ denoting male animals beside their uncompounded equivalents (see cock n.¹ 7, cock n.¹ and int. Compounds 1b).In sense 4 perhaps so called on account of its brown and stubby appearance, but possibly a different word.

Etymology: < roach n.³, after roach mane n., roached adj. 2.