“mujahideen” is the plural form. “Mu-” prefix is like the “-er” suffix in English-—it converts the verb into the noun, like teach becomes teacher, work becomes worker.
J’h’d’ is the root of ‘holy war’, or to wage war. Placing the “mu-” prefix on it makes it “holy warrior”. Mujahad. The “-een” is the plural form. Dummy is saying he is a “holy warriors”, apparently.
Funny...I got that too.
It is sort of like the “im” plural form in Hebrew.