Ruby variable name with double underscores

Question

Sometimes I see variable names with double underscore in the beginning and the end. For example:

Article.__elasticsearch__

Is there some naming convention related to double underscores in Ruby variable names?

Answer 1

An initial underscore or double underscore basically indicates "special/avoid overwrite" --meaning it's meant to reduce the likelihood that someone else might define a method/attribute of the same name. The most common occurrence is __send__.

From Ruby Forum

Answer 2

The author of the ElasticSearch gem made the wrong call IMO. At the end of the thread, Avdi Grimm, who is well-known in the Ruby community, disagrees with the OP.

There's a reason you hadn't seen it yet and that it looks odd to you. It's because it's unidiomatic.