Shamsunnahar
Literally it combines Arabic 'Shams' (sun) and 'al-Nahār' (the day) to mean 'Sun of the Day'. This construction is common in South Asian Muslim naming practice.
It is an Arabic compound (شمس النهار) used as a personal name; while the elements are Arabic, the full-name usage Shamsunnahar is especially common in Bengali-speaking Muslim communities.
It is a traditional and recognizable name in Bangladesh and among Bengali Muslims, though not among the most common contemporary choices—hence its classification as relatively rare/scholarly.
Common diminutives and affectionate short forms include 'Shamsa', 'Nahar', or 'Shamu' depending on family preference and regional vernacular.
The components 'Shams' and 'Nahar' are Arabic words used in the Quranic language, but 'Shamsunnahar' as a compound given name is a cultural usage rather than a Quranic personal name; there is no specific Quranic verse prescribing this name.