Where does “demonstrate” come from?

Demonstrate comes from Latin demonstrāre, composed of the prefix de- and the root monstrāre, ultimately descended from Proto-Indo-European de.

demonstrate (English): to show how to use; to show the steps taken to...

Definitions

Step	Language	Word	Meaning
1	Latin	demonstratus	shown, having been shown; proven, having been...
2	Latin	dēmōnstrō	—
3	Latin	dē-	—
4	Latin	dē	—
5	Latin	post	behind; after, since, besides, except; behind,...
6	Latin	poste	ablative singular of postis
7	Proto-Italic	posti	—
8	Proto-Indo-European	pósti	—
9	Proto-Indo-European	pós	afterwards, post; by, at

demonstrate — Etymology, Origin & Word History | Etymology Explorer