Real Bible Translation - Galatians 2:21

The noun δωρεά (gift, grant, favor) derives from δίδωμι (“to give”) and is morphologically parallel to θυσία : θύω, ἱκεσία : ἱκνέομαι, etc. The related adverb δωρεάν (“as a gift, freely, without payment”) is already well attested in Classical and Koine usage, and its semantic field is notably restricted:

Domain	Meaning	Example
Material gift	a physical present, offering, grant	Hdt. 6.130 — τάλαντον ἀργυρίου δωρεὴν δίδωμι
Abstract favor or privilege	a gracious benefit, often divine	Plato, Leg. 844d — διττὰς ἡμῖν δωρεὰς ἡ θεὸς ἔχει
Adverbial δωρεάν	(a) “gratuitously,” i.e. without charge; (b) “in vain” when negated by context	Dem. 19.170 — ἔδωκα δωρεάν τὰ λύτρα

Primary (Classical) Sense: Gratuitously, Without Payment

δωρεάν from δωρεά (“gift”) keeps its literal adverbial sense “as a gift,” i.e. without payment, gratis.

μηδὲν δωρεάν πράττειν (Plb. 18.34.7) – “to do nothing freely.”
ἰατρὸς δωρεὰν ἰώμενος (Aesop. 22.6) – “a physician treating without fee.”
δωρεάν λειτουργεῖν (Priene inscription, IV BCE) – “to serve the public without pay.”

This is the literal and oldest meaning, fully aligned with the noun’s sense δωρεά = a gift, a favor.

The sense “without cause / in vain” in δωρεάν is a deviant semantic "extension" arising from Hebraic calquing of חנם in the Septuagint and perpetuated by translators of the New Testament.
It does not represent natural development within Greek semantics but an imposed equivalence resulting from bilingual interference.

Greek and the New Testamet already had native expressions for “in vain” or “to no purpose” (See μάτην, used in Matt. 15:9, Mark 7:7).

So this LXX/NT usage of δωρεάν to mean “in vain, without cause” is redundant from a strictly Greek perspective — it’s purely a translation-driven semantic extension under Hebrew influence. It didn’t evolve naturally within Greek; it’s foreign imposition onto an existing lexical field.