README: Mention xv6, notes on terminology from xv6 book

README.md

@@ -1,5 +1,7 @@
 # Neptune Kernel
 
+Inspired by xv6
+
 For a quick reference on RISC-V assembly:
 - https://risc-v.guru/instructions/
 
@@ -9,6 +11,10 @@ Toolchains:
 
 ---
 
+> A word on terminology: Although the official x86 term is exception, xv6 uses the
+> term trap, largely because it was the term used by the PDP11/40 and therefore is the
+> conventional Unix term.
+
 | Register    | Name                       | Privilege Level | Description                                                                 |
 |-------------|----------------------------|------------------|-----------------------------------------------------------------------------|
 | `mstatus`   | Machine Status Register    | Machine          | Holds global interrupt enable, previous privilege mode, etc.                |