כַּדְכֹּדkadkôd

a sparkling gem, probably the ruby

Pronunciation: kad-kode' · Hebrew/Aramaic (Old Testament) · H3539

Meanings

a precious stone, perhaps ruby (Ezekiel 27:16; Isaiah 54:12)

Same root

כַּדkad · H3537properly, a pail; but generally of earthenware; a jar for domestic purposes
כִידוֹדkîydôwd · H3590properly, something struck off, i.e. a spark (as struck)

Where it appears

Appears 2 times in the Bible.

Isaiah 54:12 I will make your towers of sparkling rubies, your gates of shining gems, and your walls of precious stones.
Ezekiel 27:16 “Syria sent merchants to buy your rich variety of goods. They traded turquoise, purple dyes, embroidery, fine linen, and jewelry of coral and rubies.

Source: Brown, Driver and Briggs, Hebrew and English Lexicon of the Old Testament (1906), public domain; markup by unfoldingWord, CC BY (github.com/unfoldingWord/Brown-Driver-Briggs-Enhanced).