French suis

← French fus (mention)

← French suivre (mention)

← Old French sui (inherited)

← Galician fun (cognate)

← Latin sum (inherited)

← Latin fuī (mention)

← Latin fuī (mention)

→ English I think therefore I am (link)

→ French être (mention)

→ French chu (compound)

→ Latin cogito, ergo sum (link)