The Spanish word 'chamaco' meaning 'child' or 'youth' comes from the indigenous Nahuatl language of Mexico. It derives from the Nahuatl word 'chamahuac' meaning 'plump, grown, or presumptuous', which itself comes from the verb 'chamahua' meaning 'to grow' or 'to mature'. The semantic shift from 'grown/plump' to 'child/youth' likely occurred as the word was adopted into Spanish, possibly because children were seen as being in the process of growing or because of their characteristically plump, cherubic features.

Since 'chamaco' comes from Nahuatl rather than Latin or Greek roots, there aren't many etymologically related Spanish words. This word is primarily used in Mexican Spanish and some other Latin American varieties of Spanish.

There are no etymologically related English words since 'chamaco' comes from Nahuatl, an indigenous Mexican language, rather than from the Indo-European language family that English belongs to. This is one of many words that Spanish acquired during the colonial period in Mexico that enriched its vocabulary with Native American terms.