The title of Gardi's smoky song, "Leña Apagada," might be translated as "Extingushed Firewood." The image is meant to be kindling that was once on fire but has been put out.
Se vistió de hielo y leña apagada.
She dressed up as ice and extinguished firewood.
[Caption 16, Gardi > Leña apagada]
The verb "apagar" means "to put out / to extinguish" (as in a fire) or "to turn off" (as in a light, an electrical appliance or a car). The opposite of "apagar" is "encender" ("to light" and "to turn on"). Here are a couple of examples:
Enciende las velas
Light the candles.
¿Apagaste las luces? ¿Y la televisión?
Did you turn out the lights? And [did you turn off] the television?
¿Puedes encender una moto sin llaves?
Can you start up a motorcycle without keys?
If you're searching around for "an on/off switch," that would be "un interruptor de encendido" in Spanish. Ready to shut down (apagar) your computer now?