Where does “libsi” come from?

libsi (Old Irish) comes from Old Irish lib, from Old Irish la, from Proto-Celtic let-, from Proto-Celtic letos, from Old Czech léto, from Proto-Slavic lěto, from Proto-Indo-European leh₁tóm.

Ancestry of “libsi”, step by step

StepLanguageWordMeaning
1Old Irishlibsecond-person plural of la
2Old Irishlawith; belonging to; among
3Proto-Celticlet-—
4Proto-Celticletosside
5Old Czechlétosummer
6Proto-Slaviclětosummer; year
7Proto-Indo-Europeanleh₁tóm—
Every word from Proto-Indo-European leh₁tóm →Every word from Proto-Slavic lěto →Every word from Old Czech léto →