From Parthian *𐫤𐫀𐫃 (tāg), attested in 𐫟𐫀𐫡𐫤𐫀𐫃 (xʾrtʾg /xārtāg/, “crown of thorns”), ultimately from Proto-Indo-European *(s)teg- (“to cover”). Related to Arabic تَخْت (taḵt, “bed, couch...”), also an Iranian borrowing; and to Aramaic תָּגָא (tāḡā).
Attested as 𐢞𐢄 (tj, “crown”) (Nabatean script) in the 4th-century Namara inscription.