The Hebrew interjection anna is an earnest, impassioned cry — a particle of entreaty meaning 'O!' 'Please!' or 'I beseech you!' It appears in fervent prayers and petitions, expressing urgent appeal before a superior or before God. It is used when the speaker is pressing hard on the mercy and grace of the one addressed.
Anna is the language of bold, desperate prayer. It appears on the lips of Moses interceding for sinful Israel (Exodus 32:31), Daniel confessing for his people, and Nehemiah pleading for Jerusalem (Nehemiah 1:5). It models the kind of persistent, passionate intercession that the New Testament calls believers to in Christ's name (Luke 18:1-8). God is moved by earnest prayer.