Where does “cinquo” come from?

cinquo (Old Portuguese) comes from Latin cīnque, from Proto-Italic kʷenkʷe, from Proto-Indo-European pénkʷe — five.

Ancestry of “cinquo”, step by step

StepLanguageWordMeaning
1Latincīnquewith dissimilation of /kʷ–kʷ/ to /k–kʷ/
2Proto-Italickʷenkʷefive
3Proto-Indo-Europeanpénkʷefive
Every word from Proto-Indo-European pénkʷe →Every word from Proto-Italic kʷenkʷe →Every word from Latin cīnque →