The Hebrew words “Urim” and “Thummim” have a couple of meanings. ‘Urim’ comes from the Hebrew word for ‘light’ (‘Or’) and ‘Thummim’ usually is translated as ‘truth’ (‘Emet’). Some have translated ‘Thummim’ as ‘innocence’ because of the closeness to the Hebrew word ‘Tamim’ (which in Modern Hebrew means ‘naïve’). In Hebrew, ‘truth’ and ‘innocence’ share a deeper meaning which relates to the concept of ‘honesty’ (‘Tam’ in Hebrew) and is strongly connected to ‘purity’ (‘Tom’ in Hebrew) as in ‘pure heart’, exactly as mentioned in the Bible:
“And in the breastpiece of judgment you shall put the Urim and the Thummim, and they shall be on Aaron’s heart, when he goes in before the LORD. Thus Aaron shall bear the judgment of the people of Israel on his heart before the LORD regularly.” (Exodus 28: 30)