Question: 'Serjeant' was formerly a word for 'barrister' or 'lawyer'. Is this same derivation?

Webster's Unabridged says that "serjeant" is just a variation of "sergeant," and that "serjeant-at-law" is a barrister of the highest rank, answering to the doctor of the civil law, out-ranking king's counsel socially but in professional rank inferior to them, and until 1846 having the exclusive right to be heard in the Court of Common Pleas.

I'd never heard of the term, and cannot fathom the relationships referred to by Webster. I send out a general call to any British barristers or solicitors. Hullloooo Ruuuumpooole ....