FOR Plato and the classical tradition the principal virtue of the thumikon is courage, andreia / ἀνδρίεα ; in Latin, fortitudo.  However, andreia / ἀνδρίεα is never used in the New Testament; and where fortitudo occurs in the New Testament Vulgate it translates the Greek word dunameis, power.

The words that convey the Christian understanding of this classical virtue are, rather, tharsos /  θάρσος, courage or confidence; and even more frequently the verb-form thareō (tharseō) / θαρρέω (θαρσέω), to be confident or courageous.

SOURCES: (1) H.G.Liddell, R. Scott. A Greek-English Lexicon. rev. H.S.Jones & R.McKenzie, (Oxford, 1940).; (2) C.T. Lewis, &. C.Short, .A Latin Dictionary. Founded on Andrews' edition of Freund's Latin dictionary (Oxford, 1879).

andreia / ἀνδρίεα, manliness, manly spirit, [opposite. deilia /δειλία, cowardice]; also of women, brave deeds

II. in bad sense, insolence

III. masculine prime of life

IV. male sexual organ

V. skill

fortĭtūdo , ĭnis, f. [fortis] , strength.

I. [most frequently] Mentally, firmness, manliness shown in enduring or undertaking hardship; fortitude, resolution, bravery, courage, intrepidness

II. [very rare] Physically . Bodily strength in men and animals.

SOURCES:  Kittel, The Theological Dictionary of the New Testament, (Eerdmans, 2000, c1964).  

IN classical Greek the basic sense of thareō / θαρρέω is “to dare,” “to be bold,” and thence “to be of good courage,” “to be cheerful,” “to be confident,” (Xenoph. Cyrop., V, I, 6; V, 1, 17; Jos.Ant., 7, 266): This gives us the further main senses of:
   a. “to trust in something or someone,” “to rely on,”
   b. “to be bold against someone or something,” “to go out bravely to.
It always means “to be of good courage,” “to be confident,” “not to be afraid.”

  The term plays some part in Plato’s Phaedrus with reference to the question of death as the severest threat to man. The discussion takes place with reference to the imminent death of Socrates The dialogue hinges on the immortality of the soul, which secures tharein / θαρρεῖν (87e, 95c), , i.e., in face of death, the severest threat to human existence, tharein / θαρρεῖν is possible through awareness of the immortality of the soul (114d).

IN the Septuagint (Greek translation of the Old Testament) tharein / θαρρεῖν is a summons which men issue to one another in times of emergency and stress and anxiety (e.g., Moses to Israel in Ex. 14:13; 20:20; Elijah to the widow of Sarepta in 3 Ki. 17:13; on the lips of the prophet in Zeph. 3:16; Bar. 4:5, 21, 27, 30). The basis of the summons is the readiness of Yahweh to help […] Ii may also take the form of a divine summons to the people (Hag. 2:5; Zech. 8:13, 15) in which God stakes His own existence by way of guarantee.

IN the New Testament tharein / θαρρεῖν is a summons on the lips of Jesus: to the man sick with palsy (Mt. 9:2); to the woman with an issue of blood (Mt. 9:22); to the fearful disciples in the storm and on His appearance (Mt. 14:27; Mk. 6:50). […] Behind the summons lies the claim of Jesus to give the necessary assurance in His life and work. The summons is dynamic evidence of the fact that in encounter with Jesus God’s action is accomplished as a liberating action. The Gospel of Jesus, which consists in both His proclamation and His action, gives joy and confidence. It chases away anxiety and distress. It brings men into the goodness of the God whom they call Father. The exalted Lord comes to Paul in prison with the same summons: θάρσει […] The disciples are constantly threatened by persecution and martyrdom in the world. They live in the situation of the parting discourses before Gethsemane. Hence they live always in anxiety. Yet they are summoned to tharein / θαρρεῖν in every respect.

They are in the hands of the Victor over the cosmos. Hence they need have no fear what the cosmos will bring. This passage is highly significant. The [pagan] Greek faced by the ultimate threat to existence, draws tharein / θαρρεῖν from what lies in himself, i.e., the immortality of his higher part, the soul, whose immortality must first be proved, however, by philosophical considerations. The Christian, on the other hand, derives tharein / θαρρεῖν from the victory of Christ which overcomes the cosmos. […]

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