bash parameter expansion pattern removal syntax mnemonics for beginners
as seen on your keyboard:
# - start
$ - here's the money
% - end
${x#ass} expands to $x with "ass" removed from the beginning of $x
${x%ass} expands to $x with "ass" removed from the end of $x

${x##*/} is like retarded $(basename $x)
${x%\.*} may get rid of file extension