A Comparative Grammar of the Modern Aryan Languages of India v2.c12.s2.39

v2.c12.s2.39

The origin of all these forms is to be sought for in the Skr. किं, an old neuter. B. किसे, H. किस, P. कास, refer back to the genitive, which in Pr. is कस्स, sometimes also कोस. H. कहा is apparently a conflation of the oblique forms g. कह, abl. कह, loc. कहिं, and क्या the ordinary modern form, from supplying the hiatus of a form कआ by य instead of ह, as in Gujarati. Prakrit has also an oblique काओ, whence Sindhi केहो by softening of â to e; from its retaining the â in the first syllable the Hindi oblique काहे exhibits a form which postulates a Prakrit काहहि.