ircII help: bind backward_word

Usage: BIND <key> BACKWARD_WORD
  Moves the cursor to the first character of the previous word.
  If the cursor is in the middle of a word, the cursor is moved
  to the first character of the same word.  If the cursor is on
  the first character of a word or on whitespace, the cursor is
  moved to the first character of the previous word.