Where does “*perθ” come from?

*perθ (Brythonic) comes from Celtic *kʷerxtā, from Proto-Indo-European pérkus, from Proto-Indo-European perkʷ- — oak.

Ancestry of “*perθ”, step by step

StepLanguageWordMeaning
1Celtic*kʷerxtā—
2Proto-Indo-Europeanpérkusoak
3Proto-Indo-Europeanperkʷ-oak

Words derived from “*perθ”

Every word from Proto-Indo-European perkʷ- →Every word from Proto-Indo-European pérkus →Every word from Celtic *kʷerxtā →