Wikipedia may elaborate for you.  I think this article is a decent  
starting point: http://en.wikipedia.org/wiki/8086

Jack's explanation isn't really complete, as the 32-bit-ness of the CPU is  
irrelevant to the actual origin of x86.  The "original" x86 CPU was the  
8086, a 16-bit CPU.  The original IBM PC used the 8088, an 8-bit version  
of the 8086 (well, it had an 8-bit data bus, anyway).  "x86" is used to  
describe the entire line of CPUs that evolved from that beginning, and/or  
the instruction set (e.g. AMD, Cyrix x86-compatible CPUs).

In other words, x86 isn't used to refer to 32-bit.  It's used to refer to  
an entire class of CPUs and their instruction sets.  The marketing  
genuises have simply complicated the issue by using x64 to refer to the  
64-bit iteration of the x86 line.  This has led to a sort of retro-active  
re-definition of x86 as meaning 32-bit, but that's not really what it  
means.

Kind of dumb, IMHO, but then I find most marketing kind of dumb (including  
the term ".NET" :) ).

Pete

The initial Intel CPU with a 16-bit bus was the 8086, then came the
80186, 80286, 80386, 80486 and the Pentium, which was sometimes called
the 80586.  So essentially the number before the 86 is just a version
number.