The surname 'Louw" is understood to have originated from Jan Pieterzoon's farm named "Louwsvliet". "Vliet" was a stream and "louw" meant lukewarm/tepid.
Aafke Margaret Louw points out that the Dutch word "louw"also refers to a tench or Tinca tinca, which is a fish of the cyprinid family also referred to as a "zeelt".