Josiah W. Gibbs gives a definition of Aramaic עַתִּיק ("Ancient") in his Hebrew Lexicon.
"עַתִּיק," in Josiah W. Gibbs, A Manual Hebrew and English Lexicon, 2nd ed. (New Haven, CT: Hezekiah Howe, 1832), 173
עַתִּיק. m. Ch[aldean]. old.
This was the Hebrew lexicon Joseph Smith had accessed to and used.