sandhi contraction
Analysis. api (and, further, even) + ssu (then, afterwards), a sandhi contraction joining the particle api with the enclitic temporal particle ssu to form a connective that marks sequential or emphatic progression in discourse.
Etymology. api derives from Indo-European *api (also), cognate with Sanskrit api and related to Greek epi (upon, besides); ssu is an enclitic particle of temporal sequence, akin to Sanskrit svá (own, self) in its function of marking focus or immediacy.
Meanings from the Digital Pāḷi Dictionary; morphology and etymology by Claude.
Lite mode — plain HTML for e-readers and old browsers. Full version