Answer:
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!!