Delphi is an Integrated Development Environment (IDE). It is started off from the Pascal language, which then became Object Pascal (Pascal with objects support). Delphi is Object Pascal running on Windows and Kylix is Object Pascal running on Linux. Delphi is not a language but nowadays it is used as synonymous to language.
In the first version of Delphi, Borland used the name Object Pascal as programming language but later it is renamed as Delphi Programming Language. Delphi is a high-level, compiled, strongly typed language that supports structured and object-oriented design. This is also easy to use Rapid Development Environment (RAD) for generating stand-alone graphical user interface programs and console applications.
The word Delphi has historical significance in Greece. Delphi is both an archaeological site and a modern town in Greece on the south-western spur of Mount Parnassus in the valley of Phocis. For details you can look into the link http://en.wikipedia.org/wiki/Delphi.
Delphi was originally developed by Borland as RAD tool and released in 1995. In 2006, Borland transferred the development group to a subsidiary company named CodeGear. Later in 2008, CodeGear has been sold to Embarcadero Technologies by Borland.