I remember reading, but I can't find the source for it now, that Anatolian merchants and gentlemen (what would today be the Turkish people) would protest when called "turks" by their colleagues in Europe; and that a "turk" was some hillbilly savage, while they are of course suit&cigar europeans. This must've been towards the Sick man of Europe period, when the Ottoman state was trying, and failing, to move from a traditional agrarian society towards a more dynamic industrial society.
I was very sure of this little anecdote, and mentioned it in front of people, but then couldn't find where I've seen it, and I think I might've been misinformed and just remembered something wrong. Was this really the case?
Generally, the ethnic label “Turk” would not be used frequently in the Ottoman Empire, in the occasions when it was used, it would often be in a rather pejorative manner. It would refer to Turcoman nomads or in later periods to Anatolian Turkish-speaking peasants who were considered ignorant. To call an elite Ottoman subject or an Istanbul gentleman a Turk would be considered an insult. This could be surprising for European travelers, because in the West, the labels Muslim and Turk would have been used nearly interchangeably at the time.
That being said, things became more complicated from mid-19th century onwards with the emergence of the Turkish national idea and the ideals related to Turkism which became popular among some intellectuals – the associations of the label “Turk” thus began to shift towards more positive connotations.
I based my answer on these sources, you could check them out: