"The AT&T syntax is nearly universal to all other architectures with the same mov order; it was originally a syntax for PDP-11 assembly. The Intel syntax is specific to the x86 architecture, and is the one used in the x86 platform's documentation."
"As of November 1971, an assembler invoked as as was available for Unix. Implemented by Bell Labs staff, it was based upon the Digital Equipment Corporation's PAL-11R assembler."
https://en.wikipedia.org/wiki/X86_assembly_language#Syntax
"The AT&T syntax is nearly universal to all other architectures with the same mov order; it was originally a syntax for PDP-11 assembly. The Intel syntax is specific to the x86 architecture, and is the one used in the x86 platform's documentation."
https://en.wikipedia.org/wiki/As_(Unix)
"As of November 1971, an assembler invoked as as was available for Unix. Implemented by Bell Labs staff, it was based upon the Digital Equipment Corporation's PAL-11R assembler."