Rudra

Namaste bhagavan visweswaraya mahadevaya
Tryambakaya tripurantakaya trikagni kalaya |
Kalagni rudraya neela kanthaya mrutyunjayaya
Sarveswaraya sadasivaya srimanmahadevayanamaha ||

Rudra - root - Rtam (dam) Samsaara dukham draava yat iti Rudrah
He destroys the sorrows of the world i.e. (Rudra).

Rudra presents Vedas to Brahma at the commencement of each Kalpa. At the beginning of Brahma, there were four rshi's - Sananda, Sanaka, Sanatana and Sanal Kumara. These four rshi's did not have any offsprings. Then the Rudra concept was conceived from within Brahma what had both male and female attributes. This Rudra concept divided itself into male and female parts first and then each of which divided itself into 11 parts - the 11 Rudras (and 11 Rudrini's they call it). Looks like the 22 pairs of chromosomes are being talked about. The 23rd set actually determining the male and female nature of the human body, which down the line is identified by Gothras. In Rig Veda 7.46, Rudra is described as armed with a bow and fast-flying arrows - Dhanvi, Banahastha, which seem to fall in line with this thought.
The 11 Rudras are as follows: 
1. Mahadeva
2. Shiva
3. Maha Rudra
4. Shankara
5. Neelalohita
6. Eshana Rudra
7. Vijaya Rudra
8. Bheema Rudra
9. Devadeva
10. Bhavodbhava
11. Adityatmaka Srirudra.

Then from Brahma Narada and Dakshya were created.

The Sri Rudram is divided into eleven sections called anuvaakas. The first and eleventh anuvaakas consisting of eleven sukthaas while the rest have 2 sukthaas.
Not until Ramayana, Shiva has been used as a synonym with Rudra.