A lot vs. Alot: 9 Grammatical Pitfalls
abbreviation of Before Christ, in chronology, attested by 1823. The phrase itself, Before Christ, in dating, with exact years, is in use by 1660s.
An abbreviation used with dates of events that took place before the birth of Jesus. b.c. stands for before Christ. (Compare a.d.; see b.c.e.)