Urdu is a New Indo-Aryan language which uses case markers to express different semantic functions. The case marker ko marks accusative and dative. It is also used to express several other spatial and temporal functions. We have studied a variety of semantic usages of ko and propose an unifying explantion of all these diverse usages. We have argued that it has originated as a spatial postposition from a Sanskrit spatial term. The non-spatial usages of ko can be explained in terms of extended meaning of its spatial origin i.e. ko marks a location in a semantic field that is a spatial field by default but can be thought as temporal or eventual field in a metaphorical or abstract way.