A Universe of Sorts

$@: target, since it looks like a target.
$<: the 1st prereq, since < points to the left.
$^: all prereqs, since ^ looks like an "upward grouping flower bracket".
$?: prereqs that are newer than the target, since ? is stuff you don't know / haven't looked at.
$*: target with suffix deleted , since we generally grep for *.c|h|, we want the * part of $@. Alternatively, * is also like a target, but only the bull's eye with the extra stuff like the suffix stripped out.

§ Make Mnemonics