nt, nom./acc. sg. + api (emphatic particle)
Analysis. cattārīsa 'forty' + api 'even, also'; the nominative neuter cattārīsaṃ undergoes sandhi before the vowel-initial particle, yielding cattārīsaṃ + api > cattārīsampi.
Etymology. cattārīsa is a compound of catta 'four' (from Proto-Indo-European *kʷetwór-, cognate with English four, Latin quattuor, Greek téssares) and ārīsa 'ten times', from ārī (tens) + -sa (suffix forming multiplicatives). The form reflects the cardinal 'forty' built as 'four tens'.
Meanings from the Digital Pāḷi Dictionary; morphology and etymology by Claude.
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