The Spanish for “chest”, pecho, sounds completely different than the English chest.
The relationship is the Latin -ct- words transforming into -ch- as Latin turned into Spanish. Thus, the pect- maps to pech- exactly. The English word, on the other hand, is taken – unchanged – directly from the Latin.
Also from the same root, in Spanish, es pechuga — the common word for the common food, “chicken breast”!