The Spanish word 'pechito' comes from combining the Spanish word 'pecho' (meaning 'chest' or 'breast') with the diminutive suffix '-ito'. The base word 'pecho' itself derives from the Latin word 'pectus', which also meant 'chest' or 'breast'. The diminutive suffix '-ito' adds the meaning of 'little' or 'small', making 'pechito' literally mean 'little chest' or 'little breast'.

This is a classic example of Spanish word formation where a diminutive suffix is added to create a more endearing or smaller version of the base word. The transformation from Latin 'pectus' to Spanish 'pecho' shows typical sound changes that occurred as Latin evolved into Spanish, with the 'ct' cluster simplifying to 'ch' and the final 'us' dropping off.

The most obvious related Spanish word is 'pecho', which is the base word meaning 'chest' or 'breast'. This is a very common word that you'll encounter frequently in Spanish. You might also see related words like 'pechera' (bib or chest protector) and 'pechuga' (chicken breast), which are both derived from the same root.

While English doesn't have direct descendants of Latin 'pectus', we do have several related technical or medical terms borrowed from Latin. These include 'pectoral' (relating to the chest), as in 'pectoral muscles' or 'pecs', and 'expectorate' (to cough or spit out), which originally meant 'to discharge from the chest'. The word 'pectus' itself is still used in medical terminology, as in 'pectus excavatum', a congenital chest wall deformity.