start an ansi-term with a reasonable name

tmacs-emacs.el

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; tmacs
(defvar tmacs--counter 0)

(defun tmacs--find-free-number ()
  (cl-do ((num 0 (+ 1 num)))
      ((not (get-buffer (format "*tmacs<%s>*" num)))
       num)))

(defun tmacs ()
  (interactive)
  (ansi-term "/bin/bash" (format "tmacs<%s>" (tmacs--find-free-number))))

(global-set-key (kbd "<f12> t") 'tmacs)