Definition - What does Bar mean?
Bar is a commonly used placeholder often used to name variables or other code elements. Arbitrary naming conventions such as this are known as metasyntactic variables.
Techopedia explains Bar
The use of bar as a placeholder is derived from the use of another such placeholder: foo. Foo is one of the earliest popular placeholders used in technology. For example, foo is used to name generic variables in a learning environment. As developers continued to use foo, some began using bar as a second placeholder, partially because of the military term fubar, which has a different meaning and connotation.
As a placeholder, bar is somewhat controversial, because unlike the frequently preceding foo, bar has actual meaning in the English language. Many developers who are native English speakers prefer to use placeholders (like foo) with no inherent meaning, such as ack, baz, fum or qux. However, because of its short length, bar meets another common placeholder criteria, as many developers prefer placeholders of three letters, versus longer strings.