How does 即 + 使 compound to mean "even"?
即 = assume

使 =  make it

即使 = assumedly make it (literal meaning)

[即使 ... 也] =  [assumedly make it .... still ]


Apply the logic in the following sentence:

有錢不賣 = have money, not sell

有錢(也)不賣 = have money  (still) not sell -- 也 is implied

(即使)有錢也不賣 - (assumedly make it that) you have money, I still won't sell --  即使 is implied

即使有錢也不賣 = even you have money. I still won't sell it to you



&quot;即使&quot; literally means &quot;assumedly make it&quot;.  The practical meaning of 即使 (even), is extended from the [即使... 也] structure

Similarly:
就算 = just count as (literal meaning) --&gt; 就算有錢也不賣 (just count it as you have money, I still won't sell it to you) = (even you have money, I still won't sell it to you)
縱使 = allow to make it (literal meaning) --&gt; 縱使有錢也不賣 (allow to make it  that you have money, I still won't sell it to you) = (even you have money, I still won't sell it to you)