Acobarde comes from the verb acobardarse, which means 'to cower' or 'to become afraid'. It's a less common, more dramatic word than simply saying 'tener miedo' (to be afraid).
In the song, the lyric "Toma mi mano y por más que me acobarde" translates to "Take my hand and no matter how much I may cower." It beautifully expresses a deep vulnerability and a willingness to overcome fear for love, making it a powerful and memorable word in the context of the song's emotional depth.
Andrés Cepeda builds this entire song on one what-if: what survives of a love if neither of you remembers falling into it. He opens by admitting his own stubbornness, "Puede que nunca lo acepte si algo me enamora" (I may never accept it if something makes me fall in love), then spends the rest of the song arguing with that line. The chorus turns it into a bet: if he and this person meet again in another life, not knowing who they are to each other, he only needs one touch to break through. "Toma mi mano y por más que me acobarde" (Take my hand, however much it scares me) is the whole plan, and a kiss from this life is supposed to still be waiting in the next one.
The bridge admits memory doesn't travel that clean. "Un cuento en el que yo me pierdo" (A story in which I get lost) is as much as he expects to carry over, details gone, feeling intact. That's why the hook keeps repeating the same small test instead of a bigger declaration: "Dime te quiero por segunda vez y sabré que te quise" (Tell me "I love you" for the second time and I'll know that I loved you). He isn't asking to remember the relationship, only for the sentence to still sound true when a stranger who used to be someone else says it.