The Spanish word 'grulla' (meaning 'crane') comes from Old Spanish 'gruya', which in turn derives from the Latin word 'grus', also meaning 'crane'. This is a straightforward evolution where the Latin term for this majestic bird was preserved through the development of the Spanish language, with some phonetic changes adapting it to Spanish pronunciation patterns.

While 'grulla' itself is a relatively simple and common Spanish word, there aren't many simpler Spanish words directly related to it etymologically. However, you might encounter related words like 'grullero' (crane operator) or 'grullada' (flock of cranes), which are derived from 'grulla'.

The English word 'crane' is not directly related to 'grulla', as it comes from different Germanic roots. However, English has borrowed some scientific terms from the same Latin root 'grus', such as the family name 'Gruidae' for the crane family of birds. The word 'gruiform' is also used in ornithology to describe crane-like birds.