Galatians 2:7

ἀλλὰ τοὐναντίον, ἰδόντες ὅτι πεπίστευμαι τὸ εὐαγγέλιον τῆς ἀκροβυστίας, καθὼς Πέτρος τῆς περιτομῆς—

RBT Greek Interlinear:

Strongs 235; alla; ἀλλὰ; but; Conj

Strongs 5121; tounantion; τοὐναντίον; on the contrary; Adv-C

Strongs 3708; idontes; ἰδόντες; those who have perceived; V-APA-NMP

Strongs 3754; hoti; ὅτι; because/that; Conj

Strongs 4100; pepisteumai; πεπίστευμαι; I have been trusted with; V-RIM/P-1S

Strongs 3588; to; τὸ; the; Art-ANS

Strongs 2098; euangelion; εὐαγγέλιον; glad tiding/gospel; N-ANS

Strongs 3588; tēs; τῆς; the; Art-GFS

Strongs 203; akrobystias; ἀκροβυστίας; acro-plug/extremity stopper; N-GFS

Strongs 2531; kathōs; καθὼς; just as; Adv

Strongs 4074; Petros; Πέτρος; Small Stone; N-NMS

Strongs 3588; tēs; τῆς; the; Art-GFS

Strongs 4061; peritomēs; περιτομῆς; circumcision; N-GFS

RBT Translation:

ἀκροβυστία acro-bystia - "Top Plug"

But on the other hand, those who have perceived that I have been entrusted with the Good News of the Acro-Plug,³ just as Small Stone of the Cutting Around.

The Acro-Plug

A fitting term to describe plugging the center of one's being, so that it is...not a drain. In this way what was an "abyss" or "bottomless pit well" now becomes a highest point yielding "sons of the highest."

Julia Smith Literal 1876 Translation:
But on the contrary, having seen that I have been entrusted with the good news of uncircumcision, as Peter of circumcision;

LITV Translation:
but on the contrary, seeing that I have been entrusted with the gospel of the uncircumcision, even as Peter to the circumcision,

Footnotes

3

Gal 2:7

The Acro-Plug

Strong's #G203 ἀκροβυστία akro-bystia. "head depth, peak depth, deep point" This is a word thought to be modified from the normal Classical Greek ἀκροποσθία akro-posthia (tip of foreskin) because posthia/peos (ποσθία/πέος) referred to the male penis and/or foreskin. The first part ἀκρο "akro" means "end, farthest point, tip, limb, extremity, rim, crest." It also can mean "citadel built on a steep rock overhanging a town."

• headland, cape, Il. 4.425, 14.36, Od. 9.285, S. Tr. 788, Pl. Criti. 111a: metaph., ἄκρην πενίης οὐχ ὑπερεδράμομεν Thgn. 619, cf. A. Eu. 562; κάμπτειν Men. 4.
• hill-top, height, Od. 8.508, Hymn.Is. 72 (pl.). 
• a mountain-top, summit: used by Hom. only in the phrase κατʼ ἄκρης from top to bottom, i. e. utterly, πόλιν αἱρέειν κατʼ ἄκρης Hdt.; so in Attic, κατʼ ἄκρας utterly, Trag., Plat. 
• the citadel of a city, Lat. arx, Xen. 

Absent any signification in this compound for the male "membrum virile" we are left with βυστία bystia. What is this? No one seems to know, and the assumption was that it came from a different pronunciation of "posthia." 

The prefix βύσ- in Greek is often associated with depth or something deep.

The Diccionario Griego-Español (DGE) provides a brief and uncertain meaning of the word βύστος (bystos), suggesting that it might mean "submerged in the depths" and notes its association with the term "καμπτός" (bent, curved) and its heavy-sounding nature, as explained in the context of the name "Ἥφαιστος" (Hephaestus) (cf. DGE βύστος).

Gemini Pro 3 AI tells us the following:

While βυστία (bystia) is not the most common form found in standard dictionaries (the standard singular noun is usually βύσμα or βύστρα), it is entirely valid as a derivation meaning "plug," "stuffing," or "bung."

Here is the linguistic breakdown of why it means "plug" and how it connects to the text of Hephaestus:

The core of all these words is the verb $\beta u\omega$ (or sometimes βυνέω), which means:

• • To stuff full.
  • To plug up.
  • To cram into.

From this verb, Ancient Greek creates several nouns regarding things that "plug" or "stuff":

• • Τὸ βύσμα (To bysma): A plug, a bung, or a cork (something stuffed into an opening).
  • Ἡ βύστρα (Hē bystra): A plug (specifically often used for ear-plugs or muzzles).
  • Τὸ βύστος (To bystos): This is the word from your previous text. It represents the action of plugging or the state of being stuffed/deep.

βυστία would function as the plural of a diminutive form βύστιον (bystion - "little plug") or a variant noun for "stuffing/plugs."

This is the fascinating etymological link to the Hephaestus text.

• • The Concept: When you "plug" something, you stuff material deep into a hole.

  • The Semantic Shift: The word for "plug" (bustos) is linguistically linked to the concept of depth (buthos or byssos - the depth of the sea).

  • Hephaestus: The text was arguing that Hephaestus's name might be related to this root because he was:

    1. Cast into the deep (sumergido en lo hondo).

    2. Associated with fire "stuffed" or hidden inside the earth (volcanic/chthonic fire).

So, if you see βυστία in a text, you should translate it as "plugs," "stoppings," or "stuffing."

Thus the word ἀκροβυστία is a combination of two elements:

• • Root: $\acute{\alpha }\kappa \rho o\nu$ (akron), meaning "tip," "point," "extremity," or "summit."
  • Root: Related to $\beta \acute{u}\omega$ (byō) and the noun $\beta \acute{u}\sigma \mu \alpha$ (býsma).
  • Meaning: "Plug," "bung," or "stopper/stuffing."

When combined, the compound word literally translates to:

"A plug or covering at the extremity/tip."

Strongs #G899 βάθος is a word meaning depth and is used in either direction: depth, height — (accusative, as measured down or up) as in "deep into the mountain" and hence,

Ω (omega) depth of the riches! Also of wisdom and knowledge... (Romans 11:33 RBT)

the deep ones of the God. (1 Corinthians 2:10 RBT)

If the author were really after "uncircumcision" he could easily have used ἀπεριτομῆς "without circumcision/cutting around."