瑜伽師地論略纂 8.101

8.101

論云「皆依四種憺怕路」者，憺怕，寂義，二釋：一、置死屍處，寂寞無人法，故名憺怕；往彼處所，故名為路。二、涅槃寂靜，名曰憺怕；作不淨觀，能得涅槃，故名為路。

The treatise says: "All rely on the four kinds of tranquil paths." "Tranquil" means peaceful. There are two explanations: First, places where corpses are deposited are quiet and deserted, devoid of human activities, hence called tranquil; going to that place is called the path. Second, the peace of nirvāṇa is called tranquil; cultivating the meditation on impurity (aśubha-bhāvanā) enables one to attain nirvāṇa, hence it is called the path.