|ט צִידֹנִים יִקְרְאוּ לְחֶרְמוֹן, שִׂרְיֹן; וְהָאֱמֹרִי, יִקְרְאוּ-לוֹ שְׂנִיר.||9 which Hermon the Sidonians call Sirion, and the Amorites call it Senir--|
Minchas Shai analyzes it. He notes that it is a sin, rather than a shin. But he is troubled by what he sees in Targum, as I will explain.
Targum Onkelos translates it normally, as:
|ג,ט צִידֹנִים יִקְרְאוּ לְחֶרְמוֹן, שִׂרְיֹן; וְהָאֱמֹרִי, יִקְרְאוּ-לוֹ שְׂנִיר.||צִידוֹנָאֵי קָרַן לְחֶרְמוֹן, שִׂרְיוֹן; וֶאֱמוֹרָאֵי, קָרַן לֵיהּ טוּר תַּלְגָּא.|
though of course we are relying now on the vowel points in Onkelos. And the same in our Mikraos Gedolos. This, then, does not tell us much. Though other variants of Onkelos (in sefarim meduyakim) have it with a samech, as Minchas Shai notes.
Meanwhile, Targum Pseudo-Yonatan and Targum Yerushalmi translate Siryon as fruit-producing mountain, or fruit-producing land. Thus, Targum Yonatan:
The Sidonaee call Hermon the fruit‑producing Mount, but the Amoraee call it the Snowy Mountain, because the snow never ceases from it either in summer or winter.
That is (reading from my Mikraos Gedolos), tavra demasrei peiroi, טוורא דמסרי פירוי.
And Targum Yerushalmi:
The Sidonaee call Hermon the fruit‑producing land, but the Amoraee call it the land which multiplies the fruits of the tree.
That is, ar'a masrei peirohi, ארעא מסרי פירוהי.
He understands this as a lashon of dropping off its (plentiful) fruit. The problem with that is that while in Aramaic it would be with a samech, as written, in Biblical Hebrew it equals נושרים with a shin rather than a sin. This would either then not match, or else it would indicate that the text before the Targumists was with a shin in Shiryon.
He salvages it with a suggestion that it should be interpreted as rotting, that fruits are rotting from the abundance of fruit, and shows how that can be a translation of הבאיש.
Meanwhile, the midrash on Shir Hashirim appears to read it as a sin, because it darshens Senir as soneh et hanir, that it hates the plough. And that would require a sin as in soneih, rather than a shin.
I don't agree with the premise of Minchas Shai's question. We are dealing firstly with a Targum which favors midrash. And midrash does not always conform to true etymology. We don't know that the Targumist thought through that the cognate of the the word he was using had a heh in Hebrew, or even if such would have occurred to him, that it would have mattered.
Furthermore, this is not what the Israelites are calling Chermon. It is was the Tzidonim are calling Chermon. And we don't know their language and alphabet. It is quite possible that just as the Shin maps to a samech in Aramaic for this root, it does so (or at least to a sin) in the Siddonite tongue as well. And even if it does not, perhaps the Targumist thought that it did, or could.