Skandapurana 4.54.135

4.54.135

bhāsanādbhartsanādbhasma pāṃsuḥ pāṃsutvadāyataḥ ..

It is called bhasma from shining (bhāsana) and rebuking [evil] (bhartsana); it is called pāṃsu because it bestows the nature of fine dust;