As for the name Billericay, the town was considered part of Great Burstead in the Domesday Book. The first mention of ‘Byllyrica’ was recorded in 1291. It’s believed to be derived from Medieval Latin, beller ca, which translates as dyehouse or tanhouse. Yes, even back then, the residents were into tanning!
All facts are from Pete May's new book The Joy of Essex (Robson Press).