Only initiated men were allowed to speak this Australian language

Damin was a ceremonial register Lardil men on Mornington Island, Queensland, learned only after an advanced stage of initiation. It compressed the language into roughly 150-200 general root words, covering the same meanings through combination alone, and used click and ejective consonants found in no other Australian language. Linguist Kenneth Hale documented it from the 1960s and called it a monument to human intellectual invention; the last initiation to pass it on was held in the 1950s.

— Wikipedia contributors, Damin — Wikipedia entry on Damin, the Lardil ceremonial register documented by linguist Kenneth Hale