In English, the Ottoman sultan was the Grand Turk (late 15c.), and the Turk was used collectively for the Turkish people or for Ottoman power (late 15c.). From 14c. and especially 16c.-18c. Turk could mean "a Muslim," reflecting the Turkish political power's status in the Western mind as the Muslim nation par excellence. Hence Turkery "Islam" (1580s); turn Turk "convert to Islam."
Meaning "person of Irish descent" is first recorded 1914 in U.S., apparently originating among Irish-Americans; of unknown origin (Irish torc "boar, hog" has been suggested). Young Turk (1908) was a member of an early 20c. political group in the Ottoman Empire that sought rejuvenation of the Turkish nation. Turkish bath is attested from 1640s; Turkish delight from 1877.
1792, "an Ottoman Turk," especially a member of the ruling dynasty; as an adjective by 1829, "relating to the empire of Turkey," from Turkish Osmanli "of or pertaining to Osman," founder of the Ottoman dynasty (he reigned 1259-1326); his name is the Turkish pronunciation of Arabic Uthman. This is the native word where English generally uses Ottoman. In early use as a noun in English often mistakenly regarded as a plural.
It was the typical name in the North and the Northern armies for a Confederate soldier during the American Civil War, and the Southern soldiers were, collectively Johnnies, generically Johnny Reb. In the Mediterranean, it was a typical name for an Englishman by c. 1800. In the Crimean War it became the typical name among the English for "a Turk" (also Johnny Turk), later it was extended to Arabs; by World War II the Arabs were using Johnny as the typical name for "a British man"). Johnny Crapaud as a derogatory generic name for a Frenchman or France is from 1818.
Johnny-come-lately "a new arrival" first attested 1839. Johnny-on-the-spot is from 1896. Johnny-jump-up as an American English name for the pansy is from 1837. Johnny-cocks, a colloquial name for the early purple orchid (Orchis mascula) is attested from 1883.