The Spanish word 'garza', meaning 'heron', has an interesting Celtic origin. It comes from a reconstructed Pre-Roman Celtic word '*karkia', which also meant 'heron'. This word evolved into 'garça' in Old Spanish, and finally became the modern Spanish 'garza'. The transformation from '*karkia' to 'garza' shows typical sound changes, where the 'k' sounds softened to 'g', and the internal cluster 'ki' eventually became 'z' in Spanish.

There aren't many common Spanish words directly related to 'garza', as it's a specific term for this type of bird that has maintained its meaning consistently throughout history.

While there aren't any common English words directly related to 'garza', English speakers might be interested to know that 'heron' itself, though from a different origin, refers to the exact same bird. The word 'garza' is sometimes used in English bird guides and naturalist texts when referring to species native to Spanish-speaking regions.