Swydd Gaer (Welsh) comes from Welsh swydd, from Middle Welsh swyð, from Proto-Brythonic *suɨð, from Latin sēdēs, from Latin sedeō, from Proto-Italic sedēō, from Proto-Indo-European sḗd- — to sit.
Ancestry of “Swydd Gaer”, step by step
Swydd Gaer traces back through two separate lines of ancestry.