Where does “tenże sam” come from?

tenże sam (Polish) comes from Polish -że, from Proto-Slavic že, from Proto-Balto-Slavic ge, from Proto-Indo-European ǵʰe — Postpositional intensifying particle: indeed, at any rate, in fact.

Ancestry of “tenże sam”, step by step

StepLanguageWordMeaning
1Polish-żeIntensifying or emphatic suffix, appended to...
2Proto-Slavicžeso that, since; "emphatic enclitic"
3Proto-Balto-Slavicge—
4Proto-Indo-EuropeanǵʰePostpositional intensifying particle: indeed, at any rate, in fact
Every word from Proto-Indo-European ǵʰe →Every word from Proto-Balto-Slavic ge →Every word from Proto-Slavic že →