term-input-filter

term-input-filter is a variable defined in `term.el'.
Its value is

#[(str)
  "\301\302\"?\207"
  [str string-match "\\`\\s *\\'"]
  3]

Documentation:
Predicate for filtering additions to input history.
Only inputs answering true to this function are saved on the input
history list. Default is to save anything that isn't all whitespace.