Armen - Is the short form of Armenian name Armenak, has no connection with armen "Armenian" or "Armenia". It is often met as well as the surname Armenyan. Petrosyan - Petrosyan, Petrosian or Petrossian (Eastern Armenian), Bedrosian or Bedrossian (Western Armenian) is a common surname in Armenia.
It is a patronymic from the Armenian first name Petros (equivalent to Peter).