Refers to the Burmese language, spoken primarily in Myanmar. ビルマ is an older name for Myanmar; ミャンマー語 is also used but less common in Japanese.
He can speak Burmese.
ビルマ語の辞書を買いました。
I bought a Burmese dictionary.
From ビルマ (Burma, from English 'Burma') + 語 (language).