The Greek deiliao means to be timid, to cower, to be cowardly — a fear that paralyzes and prevents faithful action. It appears only once in the New Testament, in one of the most direct commands against fear in all of Scripture.
Deiliao appears in John 14:27, where Jesus contrasts His gift of peace with the world's peace: 'Do not let your heart be troubled and do not be deiliao.' The word is stronger than the ordinary Greek for fear (phobeo) — it describes the cowardice that causes a soldier to flee or a disciple to recant. The related noun deilia appears in 2 Timothy 1:7 — 'God has not given us a spirit of deilia (cowardice/timidity) but of power, love, and self-discipline.' And in Revelation 21:8, the deiloi (cowards) are listed first among those who do not inherit the kingdom — suggesting that fear-driven faithlessness is treated as a serious spiritual failure. The antidote is not self-generated courage but the Spirit of God and the knowledge of whose we are.