The Spanish word 'cloro' (meaning 'chlorine') traces its origins back to the Ancient Greek word 'χλωρός' (khloros), which meant 'light green' or 'yellowish-green'. This Greek word was adopted into French as 'chlore', and then made its way into Spanish as 'cloro'. The connection between the original meaning of 'yellowish-green' and the modern element chlorine comes from the characteristic pale green color of chlorine gas.

Some related Spanish words include 'clorofila' (chlorophyll), which refers to the green pigment in plants, and 'clorado' (chlorinated), as in water treatment. These words maintain the connection to both the chemical element and the original Greek meaning of a greenish color.

English speakers can easily remember 'cloro' by connecting it to several similar English words: 'chlorine' (the same chemical element), 'chlorophyll' (the green pigment in plants), and 'chlorinate' (to treat with chlorine). All these words share the same Greek ancestor referring to a greenish color. The spelling difference is minimal - English uses 'ch' while Spanish simplifies it to 'c'.