Appears to derive as the 連用形(ren'yōkei, “continuative or stem form”) of now-obsolete verb 疼ぐ(hīragu, “to hurt with a stingingpain”), in reference to the sharp thorns on the leaves.[2]
(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium. Particularly: “extend for "spotnape ponyfish" sense”)
As with many terms that name organisms, this term is often spelled in katakana, especially in biological contexts (where katakana is customary), as ヒイラギ.