This is the 5758th most frequent Catalan word.
forqué
"Forqué" in Catalan refers to a "pitchfork" or a similar forked tool.
In this sentence, 'perquè' is used as a noun, equivalent to 'reason' in English, preceded by the definite article 'el'.
No entenc el perquè de la seva decisió.
I don't understand the reason for their decision.
Here, 'per què' is used as a question to ask for a reason.
Per què has arribat tard?
Why did you arrive late?
In this context, 'per què' introduces an indirect question regarding the reason for an action.