Stir up (1326) (diegeiro from dia = through + egeiro = awaken, raise, rouse) in the active voice means to cause to wake up or to awaken (as in Lu 8:24) and in the passive voice to become awake. Figuratively it was used of a of a calm sea become stormy or turbulent, a picture the author would have been quite familiar with. Another figurative use is in reference not to the sea but to mental activity to be roused or stirred up (as in the present verse). Diegeiro is used 7 times in the NT in the NASB... Matthew 1:24 And Joseph arose from his sleep, and did as the angel of the Lord commanded him, and took her as his wife, Mark 4:37 And there arose a fierce gale of wind, and the waves were breaking over the boat so much that the boat was already filling up. 38 And He Himself was in the stern, asleep on the cushion; and they awoke Him and said to Him, "Teacher, do You not care that we are perishing?" 39 And being aroused, He rebuked the wind and said to the sea, "Hush, be still." And the wind died down and it became perfectly calm. Luke 8:24 And they came to Him and woke Him up (diegeiro), saying, "Master, Master, we are perishing!" And being aroused (egeiro), He rebuked the wind and the surging waves, and they stopped, and it became calm. John 6:18 And the sea began to be stirred up because a strong wind was blowing. 2 Peter 1:13 (note) And I consider it right, as long as I am in this earthly dwelling, to stir you up by way of reminder, 2 Peter 3:1 (note) This is now, beloved, the second letter I am writing to you in which I am stirring up your sincere mind by way of reminder, Rienecker says the preposition "dia" in this compound is "perfective" conveying the idea to stir up or wake up thoroughly. Kenneth Wuest agrees writing that "the prefixed preposition (dia) adds the idea of doing a thorough piece of work in arousing their minds". (Wuest, K. S. Wuest's Word Studies from the Greek New Testament: Eerdmans or Logos In sum, diegeiro means to awaken out of literal sleep. Figuratively as used twice by Peter, diegeiro means to arouse or stimulate to mental action. And so it means to stimulate one's thinking or to refresh their memory. Peter knew that our minds have a tendency to get accustomed to truth and then to take it for granted. We forget what we ought to remember and remember what we ought to forget! We are in a spiritual war, stakes are high & we face a deadly deceptive foe. Peter says it is duty (cf Luke 22:32) to continually (present tense) shake his readers out of their lethargy, to agitate them and arouse them fully out of their somnolent state. There is a similar idea in Peter's first epistle... Therefore, gird your minds for action, keep sober in spirit, fix your hope (aorist imperative - do it now!) completely on the grace to be brought to you at the revelation of Jesus Christ. (see note 1 Peter 1:13) Be of sober spirit (aorist imperative - do it now!) be on the alert. (aorist imperative - do it now!) Your adversary, the devil, prowls about like a roaring lion, seeking someone to devour. (see note 1 Peter 5:8) Paul issues similar calls to stir up believers... And this do, knowing the time, that it is already the hour for you to awaken (egeiro) from sleep; for now salvation is nearer to us than when we believed. (see note Romans 13:11). For this reason it says, "Awake (egeiro - present imperative), sleeper, and arise (aorist imperative - do it now!) from the dead, And Christ will shine on you." (see note Ephesians 5:14)