As far as I understood it, it meant 'to act' generally, or 'determine one's own fate/conduct'

Think maybe it was along the same lines as "finishing in the paint"?

Forgive the long post, but i thought some of you might find this humorous. it was written by my friend Duncan a couple of years ago when i alerted him to a message board discussion wherein some expectant parents were trying to decide among Hunter, Dylan and Duncan for their baby's name (and it concludes with the "finishing in the paint" reference):

http://www.babycenter.com/tips/10054.html

I can't speak for the Hunters and Dylans
of the world, but with 28 years as a "Duncan"
under my belt, I feel pretty qualified to
respond to this thread. :-)

Please don't name the child Duncan. I've
met only three other Duncans, and we all
cherish the relative exclusivity. I don't
know what I'd do if it got trendy, as I
consider "Caitlin," for instance, to be more
a sentence than a name. [Simmer down, soccer
moms; I have nothing against the name
Caitlin/Catelyn/Kaightlynneh /per se/, but do
feel sorry for the kids who are doomed to
life with an appositive. My mother, the
third Betty in her first grade class, took to
spelling her name "Bettye," I suspect in
hopes of ditching the "Red-haired-" prefix.
It didn't work.]

Indeed, Duncan was easy fodder for the
teasing kids in Elementary school and I hated
it as a child. Kids will always find
something to pick on, though, and there are
plenty of other edges to catch. It's not as
if you can prevent your child from tripping
on the playground, stuttering, or packing on
a little baby fat, in an attempt to shield
them completely from teasing. Also beyond
your control is the emergence, to your
child's schoolmates' delight, of a media
figure who happens to share your his name. I
suspect it's all character-building, anyway.

For an uncommon name, Duncan is
encumbered with a surprising retinue of
associations. I've found this saves me a lot
of time at parties. Rarely, after I
introduce myself, the new acquaintance will
cite Shakespeare; I'm impressed. Not as
impressed as if my name were Aguecheek, but
impressed nonetheless. If the citation is of
Frank Herbert's _Dune_ series, I'm intrigued,
and "Man-at-Arms" from the "He-Man"
cartoon
series at least makes me chuckle. Anyone
who's noticed that virtually every parking
meter in this country was manufactured
by "Duncan" must be keenly observant, if
nothing else. Such people warrant some
attention, at least until it is established
that they aren't carrying a pad of parking
tickets. Should the first association be
with yo-yos, cake mix, or donuts, I wonder
why my host didn't take more care with the
guest list.:-)

Entertaining, too, are the creative
spellings of Duncan I've begun to notice
lately. Whether this reflects a decline in
the advertising budget at Aurora Foods,
Sandy's advancing years, or the state of
secondary education in this country I can not
say, but "Dunken" has recently edged
"Dunkin"
as the name most commonly ascribed to me by
clerks, counter-help, and waitresses. Not as
bad, perhaps, as the plight of an associate,
one Dr. Gonzales, whose communications from
our department secretary come addressed
to "Hosa," but surprising, nonetheless.

Be aware, too, that Duncan Sullivan will
just as often be Sullivan Duncan, though the
same would apply to each of your other
choices. If the subject comes up, assure him
that his name, whichever it is, is better in
this respect than "Phillip Michael
Thomas," "Anthony Michael Hall," or
"Jan-
Michael Vincent."

So, Dorky? Perhaps. But way cool if he
can finish in the paint.