How does the repetition of the lines " brennan on the moor, brennan on the moor, / bold and undaunted stood young brennan on the moor

The effect of the repetition of lines of the poem Brennan on the moor "Brennan on the moor, Brennan on the moor / bold and undaunted stood young Brennan on the moor" has the meaning that Brennan is most undefeatable opponent and that the narrator wanted the reader to remember Brennan as a mighty warrior.