The wise king said, “A word fitly spoken is like apples of gold in vessels of silver” (Prov. xxv. 11). Hear the explanation of what he said:–The word maskiyoth, the Hebrew equivalent for “vessels,” denotes “filigree network”–i.e., things in which there are very small apertures, such as are frequently wrought by silversmiths. They are called in Hebrew maskiyyoth (lit. “transpicuous,” from the verb sakah, “he saw,” a root which occurs also in the Targum of Onkelos, Gen. xxvi. 8), because the eye penetrates through them. Thus Solomon meant to say, “just as apples of gold in silver filigree with small apertures, so is a word fitly spoken.”
Maimonides, A Guide for the Perplexed.