ἢ (ἠὲ) . . . ἦ (ἦε), or ἦ (ἦε) alone, occurs in Homer, who does not use πότερον. Thus, ἤ ῥά τι ἴδμεν ἐνὶ φρεσίν, ἦε καὶ οὐκί; do we know aught in heart,
a. All the ancient grammarians attest the accentuation of these particles as given above. Modern editors often adopt other accents. ἠέ and ἦε are derived from ἠ-ϝέ and ἦ-ϝε (whence ἤ and ἦ). With this enclitic ϝέ, cp. Lat. -ϝε.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].