vasaṁ

accusative singular of vasaṁ (indeclinable noun); or dependent genitive form 'under the control of' used adverbially

under the control of
in the power of
subject to

Analysis. Likely from a root meaning 'dwell' or 'stay', but the adverbial accusative form has become lexicalized as a postposition governing the genitive: 'X vasaṁ' = 'under the dominion/control of X'.

Etymology. Related to √vas 'dwell, stay' (Sanskrit vasati, English 'was', German 'wohnen'). The accusative frozen in adverbial use echoes the spatial imagery: 'within the dwelling-place of' → 'under the power of'.

Meanings from the Digital Pāḷi Dictionary; morphology and etymology by Claude.

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