Du or de le

https://www.wordreference.com/fren/diane

Sonnerie militaire

Bonne journée

Jim

“la diane” is a type of monkey, or equivalent to the English military related word ‘reveille’. 

Diane, capital and no article, is a French proper noun.  

Not sure if you are querying how a word has different meanings ?  English, of course, also has words with different meanings, including as verb, noun or proper noun  - rose/Rose; bob/Bob etc

There was supposed to be a photo of a street sign reading “PASSAGE de le DIANE”  the puzzle was why  ‘le’ as both the name and reveille are ‘la’ and why ‘de le’ and not ‘du’

Ah, that makes more sense. An internet search reveals it should probably be ‘ le passage de “Diane” ‘ - a named tropical storm of 2020. Even if not that - and there are other possibilities without knowing the context/photo, there would be no article indicated before Diane (in any I found anyway).