Etymology of "Osmanlı"
So, the turkish word Osmanlı means Ottoman. The thing I find interesting is that it contains the founder's name, Osman.
The part I linked to tries to explain how the name Osman turned into Ottomanus, which is probably how English gets "Ottoman".
My question is, does the suffix "lı" mean anything? I guess it's interesting that in English we took out the "us" from "Ottomanus" and derived Ottoman, while Turkish added a suffix.
I'm not Turkish, but I'll try and explain based on my knowledge.
The suffix 'lı' means 'with'. So, for example "şekerli çay" means "tea with sugar"; "peynirli ekmek" means "bread with cheese". But it's also used to turn certain nouns into adjectives. For example: "başarılı insan" means "successful person", where "başarı" means success. This is also sometimes used to express nationalities, places of origin or affiliations where there isn't already a dedicated word. For example: "Mısırlı adam" is "Egyptian man", where "Mısır" is Egypt; "Süriyeli kadın" is "Syrian woman", where "Süriye" is Syria. This also applies to cities and regions: "Istanbullu" is "someone from Istanbul", "Rizeli" is "someone from Rize", "Karadenizli" is "someone from the Black Sea region".
So the phrase "Osmanlı" follows this last usage, where the word is describing those who are affiliated with Osman.