Parallel
Hebrews 12:27
Robinson-Pierpont Byzantine Textform · Berean Standard Bible
Τὸ δέ, Ἔτι ἅπαξ, δηλοῖ τῶν σαλευομένων τὴν μετάθεσιν, ὡς πεποιημένων, ἵνα μείνῃ τὰ μὴ σαλευόμενα.
The words “Once more” signify the removal of what can be shaken—that is, created things—so that the unshakable may remain.