कोसी कलाँ kosī kalān is a small town and a train station in Mathura District of Uttar Pradesh (India). The second part of its name – kalān (big) is a common place name suffix found in northern India, Pakistan & Afghanistan. It is usually attached to place names to demarcate larger segment of a town or village in opposition to another place name suffix khurd (small). Kalān & Khurd both are Persian words, while Kalān (big, great) has been traced back to Parthian, an extinct Middle Iranian language. Khurda is related to Sanskrit Kshudra क्षुद्र (small).
In India there are several villages or towns having similar names with this distinctive opposition such as ṭīkarī kalān & ṭīkarī khurd of Delhi. This relationship between Kalān and Khurd segments of a place is somehow like a parent and child, and not necessarily bigger or smaller. The suffix Kalān (great, big) is also sometimes used with other entities such as a mosque (Kalān Masjid) or even a Person’s name (as in Khwaza Kalān).
Interesting to know that the ancestral home of Indian revolutionary Bhagat Singh is Khatkar Kalan, Punjab (India).