ने

The dropping of the initial ka- syllable in नै (nai) < कनै (kanai) has been argued to be part of a general process by which initial syllables with k- could be deleted in Western Indo-Aryan. Compare Old Rajasthani सिउ (siu) < किसिउ (kisiu, “what?”) and Gujarati શું (śũ) with Hindi कैसा (kaisā). The particle in Old Rajasthani, which had primarily ablative/dative meaning, is attested with agentive usage. Such range in function between agentive/ergative and dative of ne/nai is the case for Gujarati, Haryanvi, and Rajasthani, but not in Hindi.

This etymology is widely accepted as it is phonologically sound and accounts for the late occurrence of ने (ne) in Hindi (and its lack in Old Hindi). For the pattern of postpositions being derived from the locative forms of terms for body parts, compare को (ko, dative postp.) < Sanskrit कक्ष (kakṣa, “armpit”). Compare Vedic Sanskrit अपिकर्णम् (apikarṇam) / अपिकर्णे (apikarṇe, “behind the ear > back > from behind”).

Unlikely to be from Sanskrit -एन (-ena, instrumental case marker). This case suffix serves the same function as Hindi ने (ne) when used with past participles in Sanskrit. However the splitting of a case marker into a postposition does not occur elsewhere in Indo-Aryan and it is phonologically implausible since Prakrit has -𑀏𑀁 (-eṃ).^[2]