Compound of sekolah menengah (“high school (US), secondary school (UK)”) + pertama (“first”), calque from Japanese 初等 (shotō, “beginner, primary”) + 中學校 (chūgakkō, “secondary (middle) school”). The post-war Japanese term is 中学校 (chūgakkō). Attested in Kanpō/Berita Pemerintah 2602 (1942).