Abbott-Smith Manual Greek Lexicon
θυρεός (G2375)
1 θυρεός , -οῦ, ὁ ( θύρα ), [in LXX for מָגֵן , צִנָּה ;] in Hom., a door-stone . In late Gk. (Polyb., Plut.), the scutum , a large oblong shield : θ. τ. πίστεως , Eph 6:16 (cf. Wi 5:20 , where ὁσιότης is likened to the ἀσπίς , the clypeus or small round shield of the light-armed soldier).†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain