In my German-Lower Sorbian dictionary under
"niedersorbisch" is given "dolnoserbski", which
seems to be a general adjective; under "sorbisch"
is given "serbski". Under "Sorbisch", the noun
used for the language per se, "serbs^c/ina" is
given. Accordingly it seems clear that
"dolnoserbs^c/ina" is the native term for Lower
Sorbian.

(Wörterbuch Deutsch-Niedersorbisch =
Ne^msko-dolnoserbski sl/ownik. Bautzen: Domowina,
1990. ISBN 3-7420-0561-8

In my Upper Sorbian-German dictionary, under
"hornjoserbs^c/ina" is given "Obersorbisch" so
there you have confirmation of that.
--
Michael Everson * * Everson Typography * * http://www.evertype.com