This is some information I got from a reliable source. Take it or leave it!
The name Oppelt is an ancient germanic/teutonic name and comes from the
christian name Albrecht. Albrecht is the newer form of the old german name
Adalberath. (Adal means noble and berath means glimmering, shiny)! There are
several different ways how to spell the name: Oppel, Appel, Oppelt, Appelt,
Apitz, Opitz, Aubert, Obert etc.!
Oppelt is a dialect and short form spoken 1,200 years ago in the middel-east
of germany, later Thuringa, Saxonia etc.! Or it is from the
Bohemian/Morawian dialect name Apezc and this means Albrecht again!
The second meaning could be that the bearer of the name is originated from
the town Oppeln (now Poland) or from Opitz (now Czech Republik)! But this is
not probable likely.