etymology - Where does the term "make sure" come from?

"Make sure" here is a command means "Be sure" or "Be certain" or in a single word "Ensure".

It does not mean "make yourself sure" but "be certain that". But you can easily replace "Make sure" in your link with "Ensure" and all of it means the same.

Interestingly the origin of ensure is attributed to "make sure".

ensure

late 14c., from Anglo-Fr. enseurer , from en- "make" + O.Fr. seur
"sure," probably infl. by O.Fr. asseurer "assure."

This link offers

Both assure and ensure came into English in the late 1300s, assure
from Old French asseurer, “to reassure, calm, protect, to render
sure,” and ensure from Anglo-French enseurer, “to make sure.”

A little more digging gives the Latin word

assecurare

which means "To make sure or safe"; to assure

from Vulgar Latin
*assecurare, to make sure : Latin ad-, ad- + Latin scrus,

So it has quite an old history in the form "make sure" derived from a single Latin word