As an English and north/Low German surname, from the noun belt.
As a German surname, short form of the old Germanic name Baldher, composed of *balþ (“bold”) + *hari (“army”). Compare Belter.
Also as a north/Low German surname, from the place name Beelte, a small town in Giesen.
As a Dutch surname Van den Belt, from the noun belt (“low hill”).

Belt (countable and uncountable, plural Belts)

A surname.
A town in Cascade County, Montana, United States.
Ellipsis of Main Asteroid Belt: a region of Solar System.
- 2016 January 15, Bryan Enk, “Belter Creole 101”, in SYFY‎:
  Believe it or not, Belter slang — or, more officially, Belter Creole — isn't a completely made-up way of communicating. It's actually a mix of several Earth languages spoken by the original settlers in the Asteroid Belt colonies — very appropriate, as the Belt is a melting pot of several different races, customs and backgrounds.

English

Dutch