Flagelarnos comes from the verb flagelar, meaning 'to flagellate' or 'to whip'. It's a strong and somewhat dramatic word that isn't commonly found in everyday conversation or many song lyrics.
In "Nos Vamos Juntos," the phrase "De flagelarnos para querernos" (To stop flagellating ourselves in order to love each other) uses this word metaphorically. It suggests a deep emotional or psychological self-punishment within a relationship, implying that the couple needs to stop hurting themselves or each other in order to truly love. This powerful imagery makes it a very memorable and thought-provoking word.
Jaguares built this one around a couple who can't decide whether to stay together or tear each other apart. The deal is set in the first line, "Nos vamos juntos" [We go together], but by the second verse they're living in "infiernos mutuos" [mutual hells], calling each other "eternas hermanas" [eternal sisters] out of habit rather than affection.
The chorus is where the song earns its title: "Me voy yendo como el mar" [I'm leaving like the sea], "lento y salvaje, como tú" [slow and wild, like you]. Love and hate arrive back to back: "Después de amarnos" [After loving each other], "nos odiamos" [we hate each other]. The closing verses ask for a truce, "vamos a olvidarnos" [let's forget], "de flagelarnos para querernos" [about hurting ourselves in order to love each other], but the song never actually promises the truce will hold.