The Spanish word 'ni' meaning 'nor' or 'neither' comes directly from the Latin word 'nec', which meant 'and not' or 'nor'. This is a straightforward evolution where the Latin word was simplified in both form and pronunciation, with the final 'c' being dropped as the word evolved into Spanish, while maintaining its core negative coordinating function.

This basic negative conjunction doesn't have many related simpler Spanish words, as it is already one of the most fundamental and shortest words in Spanish. It's often used in pairs as in 'ni...ni...' to mean 'neither...nor...'.

While English 'neither' and 'nor' serve similar functions to Spanish 'ni', they are not etymologically related - they come from different Germanic roots. However, English words with the Latin negative prefix 'nec-/neg-' such as 'negate', 'neglect', and 'negative' do share a distant relationship with 'ni' through their Latin origins, though these connections might be less helpful for remembering the Spanish word due to their different uses.