Orlah refers to the foreskin — the skin removed in circumcision — and by extension to anything 'uncircumcised' or closed off. It appears about 16 times. Beyond the physical, the OT speaks of 'uncircumcised hearts' (Leviticus 26:41), 'uncircumcised lips' (Exodus 6:12), and 'uncircumcised ears' (Jeremiah 6:10) — using orlah metaphorically for spiritual imperviousness.
The removal of orlah through circumcision was the covenant sign between God and Abraham (Genesis 17) — a physical mark of belonging to God's people and cutting away of the flesh. The metaphorical uses are theologically profound: Moses fears his 'uncircumcised lips' are inadequate to speak for God; Jeremiah laments that Israel's ears are 'uncircumcised' and cannot receive God's word. Deuteronomy 10:16 commands 'circumcise your hearts' — the real transformation is not physical but inward. Paul in Romans 2:28-29 and Colossians 2:11 fulfills this logic: true circumcision is of the heart by the Spirit, not the flesh. Christ's death is described as a 'circumcision not performed by human hands' (Colossians 2:11).