The Spanish word 'tuco' comes from the Quechua word 'tucu', meaning 'bright' or 'shining'. In Spanish, the word evolved to specifically refer to a luminous insect. This is a great example of how Spanish incorporated words from indigenous American languages, in this case narrowing the meaning from a general concept of brightness to a specific glowing creature.

Since 'tuco' comes from Quechua rather than Latin or Greek roots, there aren't many common Spanish words that share its etymology. This is typical of words that Spanish borrowed from indigenous American languages.

There aren't any etymologically related English words since 'tuco' comes from Quechua, a Native American language family that didn't influence English vocabulary. English words for luminous insects, like 'firefly' or 'glowworm', have completely different etymological origins.