Source of the term is obvious - sick brain. Word "battle" before "rifle" in some official sources mean "used in battle". This word is used to separate battle rifle from sport or hunting rifle. In Russian state standard are definitions for terms "battle small-arm","sport small-arm","training small-arm","hunting small-arm".
Most fun is that this bullshit article exists 5 years and have many cross links. Very very good indicator for knowledge level of the wikipedia editors. Viva wikipedia! 69.141.140.192