It's just a saying.

[Kell shrugs. He peers over the edge of their sorry excuse of a water source.]

You can rest. With the rate it's going, it will take time to get anything out of it that's not just mud.

[He cannot sit still. Not until he drops of exhaustion at various points of day or night. He's like a candle burning from both ends, jittery and feverish.]

How did they get to you?