Apparently, from this site, it is a name on its own. The site said it's often mistaken as being short for Lancelot. Lance means "territory" in German and "lance" (a weapon) in French. It also could be a form of "Lanzo," which is Italian.
"Lance" means nothing in German, as far as I know.
German Lanze 'lance' is borrowed either from French lance or Latin lancea. I am not sure what the site is trying to say about the German name Lance, which I assume is from the same source.
Interesting. When I put "territory" into Google translator, for English to German, "lance" doesn't appear. But when I put "lance" in for translation from German to English, it says it means "territory." link
I must have done something wrong because when I put "lance" into Google translator today, it comes up "lance." Even my link today says "lance," which makes me look like a liar. Last night when I clicked that same link (above), after posting it, it said "territory"...unless of course I am losing my mind, which I most definitely could be, having had another birthday and all.
When I put "lance" into another online translator, it comes up "lanze."