Lexical Definition

‎ῥακά‎ rhaká (rhak-ah') fool ^A:N
of Chaldee origin (compare ‎רֵיק‎)

Raca.

• O empty one, i.e. thou worthless (as a term of utter vilification)

Abbott-Smith

* ῥακά (T, ῥαχά),
usually taken to represent the Aram. רֵיקָא, a shortened form of רֵיקָן, "empty," as vocalized in the Galilæan dialect; an expression of contempt, raca: Mt 5:22 (cf. DB, iv, 191 f.; and for other explanations, v. Zorell, s.v.).†

Abbott-Smith References