Loggenberg means of the hill, it is dutch originally, used to be Van Loggenberg, wa then shortened to Loggenberg when they trekked across to South Africa, been a common name in South Africa ever since, I too am a Loggenberg, my father is South African.
It definitely does not mean "of the hill". The only part of it somewhat related to a hill is "berg" and as we all know there are many surnames/last names with berg in it.