It was pronounced 'Chengis'. The term Chengisxhan was a title adopted at the all-tribal council which elected him ruler of high Asia around 1206, or 'ruler over all such as live in felt tents'. The man's giv en name was Tem-ujin.
The guy was the ultimate self-made man. His conquest of Northern China and the later conquest of all of China by his dynasty should in theory have been impossible since there was a population differential of at least 100/1 between China and Mongolia. Kind of like a squirrel killing a lion and eating it.