bum

bum  1. vt. To make highly efficient, either in time or
   space, often at the expense of clarity.  "I managed to bum three
   more instructions out of that code."  "I spent half the night
   bumming the interrupt code."  In {elder days}, John McCarthy
   (inventor of {LISP}) used to compare some efficiency-obsessed
   hackers among his students to "ski bums"; thus, optimization
   became "program bumming", and eventually just "bumming".  2. To
   squeeze out excess; to remove something in order to improve
   whatever it was removed from (without changing function; this
   distinguishes the process from a {featurectomy}).  3. n. A small
   change to an algorithm, program, or hardware device to make it more
   efficient.  "This hardware bum makes the jump instruction
   faster."  Usage: now uncommon, largely superseded by v. {tune}
   (and n. {tweak}, {hack}), though none of these exactly
   capture sense 2.  All these uses are rare in Commonwealth hackish,
   because in the parent dialects of English `bum' is a rude synonym
   for `buttocks'.