Etymology
אֱמוּנָ֖הemunah: from Heb.אָמַן aman and this from the rootא-מ-ן: to confirm, to bear. Whence alsoאֱמוּנִים emunim (trustworthy), אָמֵֽן amen (so be it) and אֱמֶ֔ת emet (steadfastness, faithfulness, truth). Cognates: Ancient Greek:ἀμήν(amḗn), Latin: āmēn
Testimonies
Alonso Schonkel's Hebrew dictionary distinguishes the following senses for the Hebrew word אֱמוּנָ֖ה, emunah:
As a human quality:
"Faithfulness", loyalty to a person or charge. Marital in Hos 2.22, social in 2Chr 19.9, to God in Eccl 45.4.
"Truthfulness", when referring to words, i.e. "speaking faithfully" (Jer 5.1; 7.28; 9.2; Ps 119.86; Pro 12.22).
"Act well," when referring to conduct, i.e., "act faithfully" (Ps 37.3 and 119.30), sometimes referring to acting well in an economic sense (2Ki 12.16; 22.7; Pro 28.20).
As God's predicate: "faithful", "loyal", "just", "righteous" (Deut 32.4; Is 25.1; Ps 89.2.3.25.34.50; Ps 96.13 and 40.11).
In the physical sense: "steadfastness", i.e. "faithfulness in the hands", in the only case where it is found that they were to be held up until sunset (Ex 17.12).
With preposition BE-Beemunah בֶּאֱמוּנָ֕ה
As an adverbial form: "faithfully", "loyally", "sincerely" (2Ki 12.16; 22.7; Is 59.4; Ps 33.4).
As adjective: "truthful" man (Pro 12.17), "faithful" friend (Eccl 6.1).
As a causative phrase: "for trusting" God (Hab 2.4).
CATALOGUE ON EMUNAH IN THE OLD TESTAMENT
HEB: Hebrew text of the Leningrad Code of 1008-1009 A.D.
LXX: Greek translation of the Seventy ➚
LAT: Latin translation of the Vulgate, a work of St. Jerome circa 400 A.D., revised by Clement VIII in 1592.
INT: literal English translation of Biblos Interlinear Bible slightly modifying the King James Bible of 1611 by a more literal translation of the Hebrew text.
SEV:Spanish translation by Bibliaparalela.com slightly modifying the 1569 Bear Bible by Casiodoro de Reina.. Exodus 17:12
HEB: וַַויְִ֥הייָָ֛דיו ֱאמוָּ֖נה ַעד־֥בֹּא ַה ָֽשּׁ ֶמשׁ
LXX: καὶ ἐγένοντο αἱ χεῖρες Mωυσῆ ἐστηριγμένα ἕως δυσμῶν ἡλίου.
LAT:Et factum est ut manus illius non lassarentur usque ad occasum solis
INT: And were his hands steady until the going down of the sun
SEV: Así (Moisés) hubo en sus manos firmeza hasta que se puso el sol
Deuteronomy 32:4
HEB: וְִִמְשָׁ֑פּטֵ֤אל ֱאמוּנָ֙הְוֵ֣איןָ֔עֶול
LXX: θεὸς πιστός, καὶ οὐκ ἔστιν ἀδικία.
LAT: Deus fidelis, et absque ulla iniquitate
INT: God of faithfulnes and without injustice
SEV: Dios de la verdad, y sin ninguna iniquidad en él
Psalm 37:3
HEB: ֶ֝֗אֶרץוְּרֵ֥עה ֱאמוָּנֽה׃
LXX: καὶ κατασκήνου τὴν γῆν, καὶ ποιμανθήσῃ ἐπὶ τῷ πλούτῳ αὐτῆς
LAT: et inhabita terram, et pasceris in divitiis ejus
INT: the land and cultivate faithfulnes
SEV: vive en la tierra, y manten la verdad
Psalm 119:30
HEB: ֶדֶּֽרךְ־ֱאמוָּ֥נה ָבָ֑חְרִתּי ִמְשָׁפֶּ֥טיךָ ִשִׁוּֽיִתי׃
LXX: ὁδὸν ἀληθείας ᾑρετισάμην, τὰ κρίματά σου οὐκ ἐπελαθόμην
LAT: Viam veritatis elegi; judicia tua non sum oblitus
INT: way the faithful have chosen your ordinances
SEV: Escogí el camino de la verdad; He puesto tus juicios delante de mí
Psalm 119:86
HEB: ָכּל־ ִמְצוֶֹ֥תיךָ ֱאמוָּ֑נה ֶ֖שֶׁקרְרָד֣פוּנִי
LXX: πᾶσαι αἱ ἐντολαί σου ἀλήθεια· ἀδίκως κατεδίωξάν με, βοήθησόν μοι
LAT: Omnia mandata tua veritas, inique persecuti sunt me, adjuva me
INT: All your commandments are faithful. A lie have persecuted
SEV: Todos tus mandamientos son [la misma] verdad; sin causa me persiguen; ayúdame
Proverbs 12:17
HEB: יָ ִ֣פי ַח ֭ ֱאמוּנָה יַ ִ֣גּיד ֶ֑צ ֶדק
LXX: ἐπιδεικνυμένην πίστιν ἀπαγγέλλει δίκαιος
LAT: Qui quod novit loquitur, index justitiæ est
INT: (He that) speaks truth, shows forth righteousness
SEV: El que habla verdad declara justicia
Proverbs 12:22
HEB: רְתּ ֹו ֲע ַ֣בת ֭יְה ָוה ִשׂ ְפ ֵתי־ ָ֑שׁ ֶקר ְוע ֹ ֵ֖שׂי ֱאמוּ ָ֣נה ְרצוֹנֽוֹ׃
LXX: βδέλυγμα κυρίῳ (יהוה) χείλη ψευδῆ, ὁ δὲ ποιῶν πίστεις δεκτὸς παρ᾽ αὐτῷ
LAT: Abominatio est Domino labia mendacia; qui autem fideliter agunt placent ei
INT: Abomination to the Lord lips lying, but they who deal faithfully are his delight
SEV: Los labios mentirosos son abominación al Señor, mas los obradores de la verdad su contentamiento
Isaiah 25:1
HEB: ִ֥כּי ָעִ֖שׂיָת ֶ֑פֶּלא ֵע֥צֹות ֵמָֽר֖חוֹק ֱא֥מוּנָה ֽאֶֹמן׃
LXX: ὅτι ἐποίησας θαυμαστὰ πράγματα, βουλὴν ἀρχαίαν ἀληθινήν γένοιτο
LAT: quoniam fecisti mirabilia, cogitationes antiquas fideles. Amen
INT: for thou hast done wonderful things, even counsels of old, in faithfulnes perfect
SEV: porque has hecho maravillas, los consejos antiguos, la verdad firme
Jeremiah 5:1
HEB: וַּבְק֣שׁוּ ִבְרחֹובֹוֶ֔תיָה ִאם־ִתְּמְצ֣אוִּ֔אישׁ ִאם־ֵי֛שׁעֶֹ֥שׂה ִמְשָׁ֖פּט ְמַבֵ֣קּשׁ ֱאמוָּ֑נהְוֶאְסַ֖לחָלֽהּ׃
LXX: καὶ ζητήσατε ἐν ταῖς πλατείαις αὐτῆς, ἐὰν εὕρητε ἄνδρα, εἰ ἔστιν ποιῶν κρίμα καὶ ζητῶν πίστιν, καὶ ἵλεως ἔσομαι αὐτοῖς, λέγει κύριος
LAT: et quærite in plateis ejus an inveniatis virum facientem judicium, et quærentem fidem: et propitius ero ei
INT: and seek in her open if you can find a man if there be any that executes judgment that seeks the truth, and I will pardon her
SEV: y buscad en sus plazas, si halláis hombre, si hay alguno que haga juicio, que busque verdad; y yo perdonaré a la ciudad
Discussion
The conceptual change did not occur with the translation from Hebrew into Greek in the Bible of the Seventy. The translators of the LXX used in 31 passages the word πίστις or a derivative to translate emunah. On fewer occasions they used aletheia,"truth". They also translated on multiple occasions אֱמֶת, emet, by πίστις. St. Jerome, when translating his Vulgate from the Hebrew and Greek, always corrected the translators of the LXX in the cases of אֱמֶת, emet, by using veritas, while on quite a few occasions when they used aletheia to translate emunah, he corrected them by resorting to fides ➚. In short, the translators of the LXX did not distinguish between אֱמוּנָה, emunah, which was closer to pistis ➚ or fides, and אֱמֶת, emot, which was closer to aletheia or veritas. This is a first cause of the conceptual shift, since the scribes of the Church of Rome who wrote the Letter to the Hebrews and Clement's Letter to the Corinthians were familiar with the wording of the Old Testament in Hebrew and Greek and were influenced by this conceptual confusion.
Now why did the author of the Letter to the Hebrews give πίστις this meaning instead of resorting to the Greek word for "belief", δόξα? In our opinion, because δόξα has a less dogmatic meaning, more akin to a simple opinion. Ancient religious thought admitted diversity of opinion when it came to questions such as the immortality of the soul (with Sadducees and Epicureans denying it, as opposed to Pharisees and Platonists, among others, affirming it; not that this meant that Sadducees and Epicureans did not believe in the existence of God or gods). Nor was the verb νομίζω, "to believe", useful, because it had reflexive overtones, such as "to consider" or "to think", which did not fit in well with the dogmatic thinking that was being tried to impose. On the other hand, πίστις could be used as the hif'il of the verb אָמַן, aman, "to confirm", because it meant "to believe" but firmly, with total certainty, or in other words, not admitting other opinions. T his kind of dogmatic thinking was emerging at the same time in the Pharisaic or rabbinical synagogues and in the Christian churches. It is no coincidence that at the same time as the Letter to the Hebrews was being written, the Sanhedrin of Yamnia promulgated the Birkat Ha Minim, or Benediction Against Heretics, ordered by Gamaliel II and formulated by Rabbi Samuel, by which Sadducees, Nazarenes and, in general, all heretics were excluded from the rabbinical synagogues. The Christian concept of heresy emerged at the beginning of the 2nd century in the Letters of Ignatius of Antioch and was developed in the second half of that century by Irenaeus of Lyon. The faith thus became a dogmatic way of thinking which did not admit diversity of opinion and which condemned the heretic or heterodox, at first, to excommunication (the herem of the rabbis, but not the biblical herem) and, later, acted violently against them.