Rig Veda I.114.5 (dedicated to **Rudra**) says

> दि॒वो **व॑रा॒ह**म॑रु॒षं क॑प॒र्दिनं॑ त्वे॒षं रू॒पं नम॑सा॒ नि ह्व॑यामहे
> । हस्ते॒ बिभ्र॑द् भेष॒जा वार्या॑णि॒ शर्म॒ वर्म॑ च्छ॒र्दिर॒स्मभ्यं॑
> यंसत् ॥५॥
> 
> We call down with reverence the ***boar of*** heaven, flame-red, with
> braided hair, turbulent in form. Bearing in his hand desirable healing
> remedies, he will extend shelter, covering, and protection to us.

In Puranas it was used to indicate the incarnation of Vishnu.

My question is - Why was the epithet varAha (वराह) used for Rudra in Rig Veda I.114.5?

**Edit 31-8-2020**

In the mantra व॑रा॒हम॑रु॒षं Can be split into varAham + aruSa . aruSa indicates **shape of a varAha**.