The words “Once more” signify the removal of what can be shaken—that is, created things—so that the unshakable may remain.
Textus Receptus (TR) - Hebrews 12:27 >Τὸ δέ, Ἔτι ἅπαξ, δηλοῖ τῶν σαλευομένων τὴν μετάθεσιν, ὡς πεποιημένων, ἵνα μείνῃ τὰ μὴ σαλευόμενα.