text: In the hymn, Rudra is described as the most dreaded terroriser (frightening). Shri Rudram describes Rudra the Vedic deity as the personification of 'terror'. The name Rudra comes from ru, meaning 'Roar or howl' (the words dreaded or fearsome could only be used as adjectives to Rudra and not as Rudra because Rudra is the personification of terror) and dra, which is a superlative meaning 'the most'. So Rudra, depending on the poetic situation, can mean 'the most severe roarer/howler' or a hurricane or tempest or 'the most frightening one'.
  Rudra and Shiva
  Shiva as known today shares many features with Rudra, and Shiva and Rudra are viewed as the same personality in Hindu scriptures. The two names are used synonymously. Rudra, the god of the roaring storm, is usually portrayed in accordance with the element he represents as a fierce, destructive deity.
  The oldest surviving text of Hinduism is the Rig Veda, which is dated to between 1700 and 1100 BC based on linguistic and philological evidence. A god named Rudra is mentioned in the Rig Veda. The name Rudra is still used as a name for Shiva. In RV 2.33, he is described as the 'Father of the Rudras', a group of storm gods.
  Hymn 10.92 of the Rigveda states that the deity Rudra has two natures, one wild and cruel (rudra), and another that is kind and tranquil (shiva). The Vedic texts  mention a horse as the vehicle (vahana) of Rudra, the "Hero on horseback" that "should be indulgent" to the singer (RV. 2.33.1). Whereas post-Vedic texts such as the Mahabharata and the Puranas mention Nandi the bull and the zebu as the vehicles of Rudra and of Shiva, thereby unmistakably linking them as the same.