cách mệnh

Etymology
This is the Northern form. Most Vietnamese nowadays are probably most familiar with this form through its usage by, and was stylized as kách mệnh in some of his books. Note that although Ho Chi Minh was a speaker of North Central Vietnamese, he rarely wrote formally in his native dialect, as is the case with other Central writers who wrote in either Northern or Southern Vietnamese.

Currently, the form with the Southern reading of the second character is more common.

Compare also the case of the title of the emperor Minh Mệnh/Minh Mạng: writers who wrote in Northern Vietnamese once preferred the former form, while the latter form was common in texts by Southern writers.