Habitarei means "I will dwell" or "I will reside." It's the future tense of the verb habitar (to dwell).
In this song, it carries a profound spiritual meaning, referencing a biblical verse about dwelling in the house of the Lord. It signifies a promise of eternal presence and security, making it a powerful and hopeful word in the context of faith.
"Comigo" means "With Me," and Leonardo Gonçalves and Kemuel build the whole song around Psalm 23 without dressing it up. The hook restates the psalm almost line for line: "Cristo é meu pastor, nada faltará" [Christ is my shepherd, I'll lack nothing]. A few lines later the song names the actual fear the psalm is answering, the valley "De morte e escuridão" [Of death and darkness], before it lands on the phrase that carries the rest of the song: "Eu não temerei, pois Tu estás comigo" [I won't fear, for You're with me].
That line repeats through nearly every verse, worn down by the end to "Ele está comigo, não há o que temer" [He's with me, there's nothing to fear]. It's built for a room to sing along with, so the repetition is the point: by the last chorus the song isn't telling you the promise anymore, it's just letting you say it back.