contigo
/konˈtiɡo/ · A1 · adv
with you
contigo = con (with) + tigo, from Latin tecum (with you)
Latin said tecum: te (you) + cum (with), the with stuck on the end. Spanish wore it down to tigo, forgot it already meant with, and added con again in front. So contigo literally says with-you-with. Same pattern: conmigo, consigo.