discard, reject, lose
丟 centers on letting something go, whether intentionally discarding or rejecting it, or unintentionally losing it.
丟 is the traditional form, with 一 on top and 去 below. The exact historical development is uncertain, but it likely relates to the idea of throwing away or discarding.
The top stroke 一 is like a lid, and the bottom 去 means 'go away'. Picture putting a lid on something and sending it away—you are discarding it.
For チュウ, imagine discarding a piece of chewing gum: chew -> チュウ, and you toss it away.