11 September 1896
In reaction to an inquiry, officials in Pretoria replied that Johannesburg was named after Johann Friedrich Bernhard Rissik and Christiaan Johannes Joubert - the only document dealing directly with the origin of the city's name. Some controversy exists concerning the origin of the name Johannesburg, as several men bearing the name Johann(es) occupied positions of authority in the Zuid-Afrikaansche Republiek (ZAR or Transvaal Republic) or were involved in events leading to the founding of the town. Rissik was a principal clerk attached to the office of the surveyor-general of the ZAR, while Joubert was a member of the Volksraad and head of the government's office of mines. It was on the recommendation of these two men that the land involved was declared a public gold-field, while they also suggested the town to be laid out either on the farm Randjeslaagte (Randjieslaagte) or a section of the farm Doornfontein. Government authorities decided on the former place. Other evidence, notably a letter from the deputy secretary of foreign affairs to the Swiss consul, dated 18 February 1896, substantiates the claim that the town was named after these two men.    
References

Potgieter, D.J. et al. (eds)(1970). Standard Encyclopaedia of Southern Africa, Cape Town: NASOU, v. 6, p. 213|Wallis, F. (2000). Nuusdagboek: feite en fratse oor 1000 jaar, Kaapstad: Human & Rousseau|Rossouw T. (2003), Die Erasmusse van Garstfontein, (Thesis), University of Pretoria, p.31