backward-word is an interactive and byte-compiled function defined in
simple.el.gz.

Signature
(backward-word &optional ARG)

Documentation
Move backward until encountering the beginning of a word.

With argument ARG, do this that many times.
If ARG is omitted or nil, move point backward one word.

The word boundaries are normally determined by the buffer's
syntax table and character script (according to
char-script-table), but find-word-boundary-function-table,
such as set up by subword-mode, can change that.  If a Lisp
program needs to move by words determined strictly by the syntax
table, it should use backward-word-strictly instead.  See Info
node (elisp) Word Motion for details.

View in manual

Key Bindings
esc-map <left>
esc-map b
evil-command-line-map S-<left>
evil-eval-map S-<left>
global-map ESC <left>
global-map M-b

References
backward-word is unused in simple.el.gz.

Find all references Functions used by backward-word

Debugging
Enable edebug
Disassemble Forget

Source Code
;; Defined in /usr/share/emacs/29.4/lisp/simple.el.gz
(defun backward-word (&optional arg)
  "Move backward until encountering the beginning of a word.
With argument ARG, do this that many times.
If ARG is omitted or nil, move point backward one word.

The word boundaries are normally determined by the buffer's
syntax table and character script (according to
`char-script-table'), but `find-word-boundary-function-table',
such as set up by `subword-mode', can change that.  If a Lisp
program needs to move by words determined strictly by the syntax
table, it should use `backward-word-strictly' instead.  See Info
node `(elisp) Word Motion' for details."
  (interactive "^p")
  (forward-word (- (or arg 1))))

Symbol Properties
byte-compile
  byte-compile-backward-word
byte-opcode
  byte-backward-word
event-symbol-element-mask
  (backward-word 0)
event-symbol-elements
  (backward-word)
evil--command-plist
  (:keep-visual t :repeat motion)
modifier-cache
  ((0 . backward-word))