sandhi contraction of kho + amhi
Analysis. kho (emphatic particle: 'indeed, surely') + amhi (1st person singular present of atthi, 'to be'). The contraction shows elision of the initial vowel of amhi after kho's final vowel.
Etymology. amhi from √as (Sanskrit asti, Latin est, English is) — the Indo-European copula. kho is a particle of assertion and emphasis, probably cognate with Sanskrit kha ('space, ether') in its sense of 'openly, clearly', reinforcing the truth-claim.
Meanings from the Digital Pāḷi Dictionary; morphology and etymology by Claude.
Lite mode — plain HTML for e-readers and old browsers. Full version