According to teh wikipedia:
The keyboard symbol for the ESC key (which may be used when the usual Latin lettering "Esc" is not preferred for labeling the key) is standardized in ISO/IEC 9995-7 as symbol 29, and in ISO 7000 "Graphical symbols for use on equipment" as symbol ISO-7000-2029. This symbol is encoded in Unicode as U+238B broken circle with northwest arrow (⎋).
I had no idea! Also, "broken circle with northwest arrow" sounds like a military code for an extremely specific kind of nuclear weapons fuckup. Did you have a "broken arrow?" A "bent spear?" A "broken circle with northwest arrow?"