BBC news has a nice outline of the functions of the Lord Chancellor, pros and cons of having one, and some history, under the heading Changes Explained / End of historic post.
The term chancellor goes back to the Latin and obviously is used in other languages too (Kanzler, Kanzlei). It’s also related to chancel, the eastern part of a church sometimes separated by screens or railings. The earliest OED etymological link is to Latin cancellarius, a court usher who sat ad cancellos or at the screen or lattice separating the judges from the public. This recalls the changes the word bar has gone through in legal English. Continue reading