Morena literally translates to "brunette" and is often used to describe a woman with dark hair or skin. It's a common term of endearment in Portuguese-speaking cultures.
In the song, the singer mentions "os olhos da morena" (the eyes of the brunette) as the reason he feels compelled to leave. This word is interesting because it's a culturally rich term that goes beyond a simple physical description, often carrying connotations of beauty and allure in a romantic context.
Have you ever felt torn between staying somewhere familiar and leaving for something new? That's exactly what D.a.M.A sings about in "Terra Da Maria"! He's holding onto dreams he's had "há tanto tempo guardados" [kept for so long] and isn't even sure where he wants to be anymore. He wants to stay, but there's something about "os olhos da morena" [the dark-haired girl's eyes] that makes him want to go.
So, he's off to "a terra da Maria" [Maria's land]! He even invites anyone who wants to come along, promising he'll be back "qualquer dia" [any day]. He remembers leaving his homeland feeling happy and full of ambition, but now he sees that "às vezes a gente erra" [sometimes we make mistakes] because "não há dinheiro que pague a paz do meu coração" [there's no money that can buy my heart's peace]. He's hoping to find open arms waiting for him, even if his childhood home isn't there anymore. It's a sweet song about the pull of home and the people who make it special.