Sitt
Yes. 'Sitt' functioned historically as an Arabic honorific and appears in medieval sources and titles (for example Sitt al-Mulk, a Fatimid regent).
No. 'Sitt' is not a Quranic proper name; its use is attested in historical and literary Arabic contexts rather than in the Quranic text.
Rarely as a modern given name; it more commonly survives as an honorific or part of compound historical names in scholarship and traditional usage.
It implies respect, seniority or rank—comparable to 'lady' or 'mistress' in English, often used for a woman of standing.
The term itself is feminine; variants in usage include extended forms like Sittah or colloquial diminutives such as Sitta in some dialects.