What underlying semantic notions connect the notion of 'thrown or hitting on both sides' to 'Amphiboly'?

Question

_{Source: p 108, With Good Reason, An Introduction to Informal Fallacies (6 ed, 2000) by York U. Prof. S. Morris Engel}

The fallacy of amphiboly* is the product of poor sentence structure. It results when words are incorrectly or loosely grouped in a sentence, giving rise to a meaning not intended by the author.

[I omit this book's deficient etymology of 'amphiboly'.]

OED redirects amphiboly to amphibole; the latter's Etymology states:

< French amphibole, 1. adj. ‘ambiguous, of a double sense’ (Cotgrave 1611), 2. the mineral;
< Latin amphibol-um ambiguous,
< Greek ἀμϕίβολ-ον thrown or hitting on both sides, ambiguous,
< ἀμϕί on both sides + βολ-, βαλ- stem of βάλλ-ειν to throw.

What underlying semantic notions connect the notion of thrown or hitting on both sides (from the Ancient Greek etymon) to the modern definition in Informal Logic?

Answer 1

Amphiboly or amphibology stays for Syntactic ambiguity, i.e.

a situation where a sentence may be interpreted in more than one way due to ambiguous sentence structure.

Ambiguity is also the word used in the translation of Sophistical Refutations:

[165b23-166a22.] Examples such as the following depend upon ambiguity: ‘I wish that you the enemy may capture.’ And ‘He who knows that, that knows’; for by this phrase one may signify as the knower either him who knows or that which is known.

The ethymology for the Ancient Greek ἀμφίβολος is:

I. put round, encompassing, Eur.

II. attacked on both or all sides, Aesch.

III. doubtful, ambiguous, Plat., Xen., etc.

Thus, we have a "shift of meaning" from II to the figurative usage III: a sentence that can be undestood in two different ways not because the words per se are ambiguous, but due to the syntactical construction of the phrase.