Meaning:
Its source is Ancel, a Norman French name meaning "Servant."
Narrative:
While this name may be derived from the Germanic name Lanzo (land), the purest and most devout of King Arthur's knights would not have hestitated to describe himself as a servant of God -- until, that is, he fell under the spell of Queen Guinevere, at which time he became a servant of a different stripe.
Also reinforcing this derivation is Shakespeare's use of the names Launce and Launcelot for servant characters in two of his plays.