Probably from the same as akmen; a thorn -- thorn.
see GREEK akmen
a. a thorn bramble-bush, brier: Matthew 7:16; Luke 6:44; Hebrews 6:8; εἰς τάς ἀκάνθας i. e. among the seeds of thorns, Matthew 13:22; Mark 4:7 (L margin: ἐπί), 18 (Tdf. ἐπί); Luke 8:14 (Luke 8:7 ἐν μέσῳ τῶν ἀκανθῶν); ἐπί τάς ἀκάνθας, i. e. upon ground in which seeds of thorns were lying hidden, Matthew 13:7.
b. a thorny plant: στέφανον ἐξ ἀκανθῶν, Matthew 27:29; John 19:2 — for bare thorns might have caused delirium or even death; what species of plant is referred to, is not clear. Some boldly read ἀκανθῶν, from ἄκανθος, acanthus, bear's foot; but the meaning of ἄκανθα is somewhat comprehensive even in secular writings cf. the classical Greek Lexicons under the word (On the