Editing Openai/69186d20-2d14-8013-b9c6-c09000f173f6 (section)

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* Modern Irish: slán “safe, whole, healthy; goodbye.”
* Old Irish: slán “whole, healthy, complete.”
'' Proto-Celtic: generally reconstructed as ''slāno- “whole, healthy.”
'' Proto-Indo-European: from ''slā- / *sleh₁- “whole, healthy, sound” (same base that gives various “whole, healthy” words across IE).

True cognates (same ancestor root, not just similar meaning):
* Old Irish / Scottish Gaelic / Manx: - ScG slàn “healthy, whole” (same word); - Manx slane “whole, entirely.”
'' In wider IE, the connection is more remote/obscure but likely related to the “whole/healthy” root that underlies sets like: - some Slavic and Baltic items with meanings “whole / healthy” (e.g. Russian целый is from another root, but there are related ''slā- etc. hypotheses – the details get technical and debated). - the secure part: Celtic branch has a clear slāno- “healthy, whole,” from PIE *slā-.

So: slán is historically an adjective “whole, sound, in one piece,” and the farewell is literally saying “(be) safe / be well,” just like English “goodbye” originally “God be with ye,” or Spanish “adiós,” “hasta luego” with similar benevolent implications.