Bacalao is the Spanish word for "codfish," a common food item. However, in this song and in some Caribbean slang, it's used as a colorful insult.
Calling someone a bacalao can imply they are undesirable or have a bad smell, much like dried and salted cod. It's a prime example of how everyday words can take on completely new, metaphorical meanings in slang, making it a fun and memorable word to learn.
Yailin la Mas Viral does not hold back in "Creta Seca." This is a full-on diss track aimed at a rival, and the lyrics are incredibly direct. The whole point is to make the other person respect her, as she repeats in the chorus: "¿Pa' que? Pa' que respete" (For what? So you respect). She uses a lot of Dominican slang to insult her rival's appearance, calling her "Creta seca" (dry hair) and "cuero ruyio" (worn-out promiscuous woman).
She's not just insulting her, though. Yailin is also bragging about her own power, especially over her rival's man. She claims, "Es que tú no corre', lo cojo cuando, yo quiera" (It's that you don't run things, I take him when I want). The ultimate burn comes when she says she was with him first and only let her rival have him after she was done: "Si lo tiene es por que quiero / Te lo deje seco y pelado" (If you have him it's because I want to / I left him for you dry and bare). It's a song about dominance, putting someone in their place, and making sure they know who is in control.