2nd person singular imperative (reading uṭṭhetha) + vocative particle āvuso; surface form uṭṭhethāvuso shows imperative uṭṭhetha with sandhi fusion to āvuso ("friend")
Analysis. uṭṭhetha (imperative of uṭṭhahati) + āvuso (vocative, "friend"); the particle transforms the command into an address: "Rise up, friend!"
Etymology. From ud- (up, out) + sthā (stand), cognate with English "stand", Latin stāre, Sanskrit sthāti. The prefix ud- reverses the simple root to mean "rise" rather than "remain standing."
Meanings from the Digital Pāḷi Dictionary; morphology and etymology by Claude.
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