Since the 19th century, Köbes is the name given to a waiter who serves beer in the brewery pubs of Cologne, Bonn, Düsseldorf or Krefeld. Traditionally he always wears a blue linen apron with a leather belt and purse.
"Köbes" is the local dialect form of Jacob and also features in other Rhineland dialects, although it is occasionally also used in the secondary meaning of a "stubborn, tenacious or square-built person".
The Köbes and their way of serving beer are part of the typical Rhineland brewery culture. If a beer glass is empty, the Köbes will bring a new glass without being asked, unless the guest places a beer mat on the glass or signals that he wants to pay. The often gruff style of the Köbes is attributed to the fact that the brewery workers brought in to work in the taproom were poorly trained in looking after visitors:
"In Cologne everything was different. […] You don't order a Kölsch in a brewery, you get it brought to you. Likewise, the Köbes is not a waiter, but a brewery worker, whose pride does not allow him to bring beer to the tables. However, when the people of Cologne stick to the rules, which is rarely enough, they do it in expectation of the exception, which says that Köbes ultimately do bring beer to the tables, because they are entrepreneurs and therefore not waiters. [..] You have to think of a Köbes in the same way as divine providence or the Archangel Gabriel. Then everything is fine."²
Source: https://www.wikipedia.org/ (Status: 24.08.2018)
² Frank Schätzing, Keine Angst (no fear), Munich 2007, p. 228 et seq.