Unfortunately, there are many possibilities and without going to historical records it cannot be easily detemined.
Dorchadas already put a lot of good facts together, read her answer first since I try not to repeat.
For places in Baden-Württemberg, there is another splitting possible: Harl-ach with ach meaning "water; creek, small river" but I have not immediate idea on harl.
Than, we cannot exclude that the place is named for a given name, there are given names ending in -lach from laic "play" like Gundlach or Gerlach. The name *Hari-laic (or a form of it) isn't attested in Förstemann 1900, but it is an entirely plausible medieval German name.
--elbowin
This message was edited 11/3/2019, 1:29 AM