A young missionary, assigned to bring religion to the Maori people, was walking down a jungle path with the chief. He and the chief were teaching one another their respective languages.
The chief would point at a rock, and say "Ugh . . . what that?" and the missionary would say "Rock" . . . the chief would repeat the word and they'd proceed along the path.
In due course, they came upon a disturbance - people moaning, bushes shaking . . . really unusual. The chief parted the bushes, and a couple very much . . . involved . . . in one another were revealed.
The chief pointed, and said "Ugh . . . what that?"
The missionary, young, inexperienced, and embarassed, said the first thing that popped into his mind: "Main riding bicycle." The chief repeated the phrase, released the bushes, and they continued, leaving the couple alone.
The next day, the missionary and chief are out for their linguistic stroll again, and, much to the missionary's dismay, they round a bend and hear moaning and see a bush shaking. Not again.
The chief parts the bushes, takes one look at the couple, and immediately kills them both with his spear.
Horrified, the young missionary asks, "Why, chief, why did you kill them?"
With an angry grimace, the chief explains: "Today, man riding MY bicycle!"