The Spanish word 'neto' meaning 'net' or 'clean' comes from the Latin word 'nitidus', which meant 'bright, clean, or pure'. This Latin word evolved into similar forms across several Romance languages, including French 'net', Catalan 'net', and Italian 'netto', all meaning 'clean' or 'clear'. The Spanish form 'neto' developed from these Romance language influences, particularly French and Catalan, while maintaining the core meaning of 'clean' or 'net' (as in net weight or net profit).

The semantic development from 'bright/clean' to 'net' (as in net amount) is quite logical - a net amount is the 'clean' or 'pure' amount after all deductions have been made.

A related Spanish word is 'nítido', which comes more directly from Latin 'nitidus' and means 'clear, sharp, or distinct'. This preserves more of the original Latin meaning of brightness and clarity. You can see how both 'neto' and 'nítido' share the concept of clarity and purity from their common ancestor.

English speakers will recognize the word 'net' as in 'net weight' or 'net profit', which is directly related to Spanish 'neto'. Both words share the same Latin origin and developed similar meanings of 'pure' or 'clean' amount. The English word was borrowed from French 'net', which came from the same Latin root 'nitidus'. Another related English word is 'nitid', though it's rather rare, meaning 'bright, lustrous, or clear' - it's a more direct borrowing from Latin 'nitidus'.