How would a student justify inferring that “indigenous” means “originating in a particular region”?

The word derives from:

'indigenus' (late Latin) -->

means 'native,' which is being born in a country/place/(particular region)

While the root word  'indigena'  ~  means 'native'

ADDITIONAL:

The root 'indu' (old Latin) --> means 'in, within' (in this case, a particular region)

The Latin 'gignere' -->

means 'to beget'  

While the root word of 'gignere' -->

'gene'   ~   means to give birth, produce, beget

These (its) root words justify the meaning of indigenous ("originating in a particular region," as you stated)

Hope this helps!!

theres no poem plesae include that