The Latin antecedent of "inexorable" is "inexorabilis," which is itself a combination of the prefix "in-," meaning "not," plus "exorabilis," meaning "pliant" or "capable of being moved by entreaty." "Exorabilis" in turn derives ultimately from the Latin verb "orare," meaning "to speak or plead." It's a fitting etymology for "inexorable." You can beseech and implore until you're blue in the face, but that won't have any effect on something that's inexorable. "Inexorable" has been a part of the English language since the 1500s. Originally, it was often applied to persons, or sometimes to personified things ("deaf and inexorable laws"). These days, it is usually applied to things, as in "inexorable monotony" or "an inexorable trend." In such cases, it essentially means "unyielding" or "inflexible."
G-d's judgment is inexorable as we read in Ezekiel:
"I, the LORD, have spoken; it is coming and I will act. I will not relent, and I will not pity and I will not be sorry; according to your ways and according to your deeds I will judge you," declares the Lord GOD.'" (Ezekiel 24:14)
And yet He is merciful and does relent when His ultimate purpose (repentance) is fulfilled:
...if that nation against which I have spoken turns from its evil, I will relent concerning the calamity I planned to bring on it. (Jeremiah 18:8)
G-d's plan of redemption cannot be foiled: it is inexorable.
So then it does not depend on the man who wills or the man who runs, but on God who has mercy. (Romans 9:16)
In this we can have confidence. To Him who began a good work in us and who will perfect it (inexorably) until the day of Messiah Yeshua be the honor and glory forever. Amen.