[acdha]

It makes more sense when you look at the history: i386 has been around for going on three decades and was originally the only x86 architecture. When the world started to go 64-bit, Intel was pushing Itanium as IA-64 as the top-performance option which could go head to head with high-end 64-bit RISC processors such as Alpha, PA-RISC, PowerPC, SPARC, etc. They attempted to rebrand x86 as IA-32 as a marketing exercise to match IA-64, both to demarcate it as the lesser architecture and to continue making the competing x86 vendors look less legitimate to business customers.

AMD was the first to develop and announce a 64-bit x86 extension back in 1999 and since they shipped the first hardware, the amd64 name distinguished it from Intel's IA-64. When Intel wrote off IA-64 and adopted AMD's extensions the “amd64” name was already used in a number of places.

[Phrodo_00]

amd64 does make sense because the distro will work in all amd64 computers (including EM64T stuff).

Calling i686 i386 doesn't, unless packages are actually compiled for i386 (which I don't think they are).