Rudra is frequently associated with the Maruts (i. 85). He is their father, and it is said that he created them from the gleaming udder of the cow Prsni. He is fierce and destructive, and is known as a bull as well as the ruddy (arusá) boar of heaven. He is exalted, the strongest of the strong, swift, unrivalled in power. He is young and unaging, a lord (sana) and the world's father. He is aware of the actions of men and gods due to his rule and universal dominion. He is plentiful (midhváms), easily invoked, and auspicious (sivá). However, he is commonly regarded as malevolent, as hymns addressed to him primarily express fear of his terrible shafts and despise of his wrath. He is urged not to slay or injure his worshippers and their possessions in his rage, but to keep his great malignancy and his cow-slaying, man-slaying bolt from them, and to lay others low. He is not, however, purely malevolent in the way that a demon is. He not only protects from disaster, but also bestows blessings. His healing abilities are frequently mentioned; he possesses a thousand remedies and is the greatest physician of physicians. In this regard, he has two distinct epithets: jálasa, which means "cooling," and jálasa-bhesaja, which means "having cooling remedies." Rudra's physical foundation is not readily apparent. However, it appears likely that the phenomenon underlying his nature was the storm, not in its pure and simple form, but in its malevolent aspect as seen in the destructive agency of lightning. His healing and beneficent powers would have been founded partly on the thunderstorm's fertilising and purifying action, and partly on the negative action of sparing those whom he might slay. As a result of his wrath's deprecation, the euphemistic epithet sivá became the regular name of Rudra's historical successor in post-Vedic legend. The name's etymological meaning is unknown, but it would be 'Howler' according to the usual derivation from rud cry.