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se (1) (Pronoun) "oneself"
From Latin se 'id.' From Proto-Italic *se 'id.' From Proto-Indo-European *se 'id.'

In Proto-Indo-European, *s(u̯)e- meant "peculiar to oneself." Derivations from *su̯e- thus connote distinctiveness from other things. Benveniste (1973) writes, "This duality survived, as is revealed by the etymology, in the two forms se of Latin, which have become independent; the reflexive se, indicating “self,” and the separative se-, sed ‘but’, marking distinction and opposition."