As a noun, "the Britons," also "the Welsh language," both from Old English. The word survives in Wales, Cornwall, Walloon, walnut, and in surnames Walsh and Wallace. Borrowed in Old Church Slavonic as vlachu, and applied to the Rumanians, hence Wallachia. Among the English, Welsh was used disparagingly of inferior or substitute things (such as Welsh cricket "louse" (1590s); Welsh comb "thumb and four fingers" (1796), and compare welch (v.)). Welsh rabbit is from 1725, also perverted by folk-etymology as Welsh rarebit (1785).
1520s, of a people of what is now souther and southeastern Belgium, also of their language, from French Wallon, literally "foreigner," of Germanic origin (compare Old High German walh "foreigner"). The people are of Gaulish origin and speak a French dialect. The name is a form of the common appellation of Germanic peoples to Romanic-speaking neighbors. See Vlach, also Welsh. As a noun from 1560s; as a language name from 1640s.
county in the far southwest of England, from Old English Cornwalas (891) "inhabitants of Cornwall," literally "the Corn Welsh," from the original Celtic tribal name *Cornowii (Latinized as Cornovii), literally "peninsula people, the people of the horn," from Celtic kernou "horn," hence "headland," from PIE *ker- (1) "horn; head, uppermost part of the body" (see horn (n.)), in reference to the long "horn" of land on which they live. To this the Anglo-Saxons added the plural of Old English walh "stranger, foreigner," especially if Celtic (see Welsh). The Romans knew it as Cornubia; hence poetic Cornubian.
1670s, "of or pertaining to the French," from Latin Gallicus "pertaining to Gaul or the Gauls," from Latin Gallia "Gaul" and Gallus "a Gaul" from a native Celtic name (see Gaelic), though some connect the word with prehistoric West Germanic *walkhoz "foreigners" (see Welsh). Originally used in English rhetorically or mockingly for "French." The cock as a symbol of France is based on the pun of Gallus "a Gaul" and Latin gallus "cock" (see gallinaceous). Earlier was Gallican (1590s).
It means not simply 'French,' but 'characteristically', 'delightfully', 'distressingly', or 'amusingly' 'French' ... not 'of France', but 'of the typical Frenchman'. [Fowler]
As "of or pertaining to the ancient Gauls" from 1796.
c. 1200, frensh, frenche, "pertaining to France or the French," from Old English frencisc "French," originally "of the Franks," from franca, the people name (see Frank). A similar contraction of -ish is in Dutch, Scotch, Welsh, suggesting the habit applies to the names of only the intimate neighbors.
In some provincial forms of English it could mean simply "foreign." Used in many combination-words, often dealing with food or sex: French dressing (by 1860); French toast (1630s); French letter "condom" (c. 1856, perhaps on resemblance of sheepskin and parchment), french (v.) "perform oral sex on," and French kiss (1923) all probably stem from the Anglo-Saxon equation of Gallic culture and sexual sophistication, a sense first recorded 1749 in the phrase French novel. (In late 19c.-early 20c., a French kiss was a kiss on each cheek.) French-Canadian is from 1774; French doors is by 1847. To take French leave, "depart without telling the host," is 1771, from a social custom then prevalent. However, this is said to be called in France filer à l'anglaise, literally "to take English leave."
"of or pertaining to the Welsh" and their kindred, the Cornish and Bretons, by 1833, from Welsh Cymru "Wales," Cymry "the Welsh," plural of Cymro, probably from ancient combrox "compatriot," from British Celtic *kom-brogos, from collective prefix *kom- (see com-) + *brogos "district," from PIE root *merg- "boundary, border." Compare Allobroges, name of a warlike people in Gallia Narbonensis, literally "those from another land." As from 1833 as a noun, "the language of the Cymry."