A "clipper" was a kind of ship used in the second half the XIX century. The choice of this name, and of other names such as "harbour", suggest that xBase programmers might have a distinctive maritime vocation.
According to the page http://en.wikipedia.org/wiki/Clipper_programming_language, "Clipper was originally created in 1985 as a compiler for dBASE III" (see also http://en.wikipedia.org/wiki/DBASE). The Clipper programming language is a superset of dBASE III+ and its success lead to similar programming languages - named xBase.
Later, the programming languages derived from the original dBASE programming language - that is, Clipper - and its database formats were names xBase (http://en.wikipedia.org/wiki/XBase, and see also http://en.wikipedia.org/wiki/Category:XBase_programming_language_family).
I read also that "A language standard committee (ANSI X3J19) was convened in 1990 to identify the common language features". dBase, Clipper, FoxBase
http://linux.techass.com/projects/xdb/xbasedocs/xbase_c1.html.
http://www.underflap.com/clipper/
At the moment, the commercial software available comprehends CA-Clipper 5.3x, Alaska Xbase++, CA-Visual Objects, Multisoft Flagship, Microsoft FoxPro, dBase.
Today there is a free dbase clone: http://dollybase.sourceforge.net/. And see also nanoBase (in the "Free Software for DOS" site at http://home.att.net/~short.stop/freesoft/dbase.htm). There is also a project to implement in a C++ class library the data structures and features of xBase (http://freshmeat.net/projects/xbase).
The reasons of the success of xBase is that it's good :-) for managing databases. See the article "Non-SQL Databases for Linux" by Christopher Browne at http://freshmeat.net/articles/view/307/. Refer also to the FAQs at http://www.davep.org/clipper/FAQ/.
The article on Freshmeat at the address http://freshmeat.net/articles/view/307/, Non-SQL Databases for Linux, is a good starting point for our xBase study. If you discover that you like very much xBase, have a look at http://www.geocities.com/tablizer/xbasefan.htm, a page for xBase fans.
Useful link are in http://www.geocities.com/SiliconValley/Lab/6888/xbasefan.htm (The xBase Fan Club), http://cbbrowne.com/info/xbase.html, http://www.melbpc.org.au/pcupdate/9100/9110article6.htm
http://linuxfinances.info/info/xbase.html
http://donnay-software.com/links.htm
http://x2c.dtop.com/more-xbase.html
http://clipperforwindows.freeservers.com/favorite_links.html