The Greek compound noun ethelothreskeia (ἐθελοθρησκεία) is formed from ethelo (to will/desire) and threskeia (religion/worship). It means self-chosen or self-imposed religious practice — worship invented by human will rather than commanded by God. The word appears only once in the New Testament (Colossians 2:23) and is likely a term Paul coined or adapted.
Paul's single use of ethelothreskeia in Colossians 2:23 is a devastating critique of false asceticism. He identifies regulations like 'Do not handle! Do not taste! Do not touch!' as ethelothreskeia — religion of human manufacture. Such practices have 'an appearance of wisdom' but lack any value against indulgence of the flesh. The theological danger of ethelothreskeia is not external practices per se but the assumption that self-invented religious activity earns favor with God. True worship is always responsive — it begins with God's self-revelation and command, not human religious creativity. Isaiah 29:13 anticipates this critique: their worship consists of 'rules taught by men.'