The Spanish word 'nene' meaning 'small child' comes from baby talk or expressive language. This is similar to how many languages have simple, repetitive syllables in words referring to parents or children (like 'mama' or 'papa') that originate from the natural sounds babies make when learning to speak.

The word 'nene' is itself a basic, child-friendly term in Spanish, so there aren't really any simpler related Spanish words. However, you might hear variations like 'nenito' or 'nenita' (with diminutive suffixes) used affectionately for very small children.

While not directly related etymologically, English has similar baby-talk derived words like 'ninny' (though this has taken on a more negative meaning) and the reduplicative 'night-night' used when putting children to bed. These showcase how different languages often develop similar-sounding childish or nursery terms independently.