I just realised that the meaning of the term "metabelian", when applied to groups, or Lie algebras, seems to have changed over years. (These days, it means that $[[G,G],[G,G]]$ is trivial, while in the past it was occasionally used to indicate that $[[G,G],G]$ is trivial. The difference here is that between solvability and nilpotence, that is.) 

<a href="http://groupprops.wiki-site.com/index.php/Metabelian_group">This</a> wiki says "The concept and term *metabelian group* was introduced by Furtwangler in 1930.
The term *metabelian* was earlier used for groups of nilpotence class 2, but is no longer used in that sense." (I don't understand "earlier" here. Can that sentence be parsed uniquely? Earlier than Furtwangler introduced the term? Earlier than the wiki article was written?)

I know at least one reference from mid 1960s where that old-fashioned usage is present, and I'd like to understand the history better in this instance. Thanks for help.