keep (one's) knickers on

To remain calm and composed while waiting for something. Usually used as an imperative. Primarily heard in UK. If all those investors would just keep their knickers on instead of jumping ship at the first sign of danger, the company might have had a chance to recover from the poor reception of their latest hardware. A: "Bill? Bill? Hey, Bill! C'mon, what's the hold up?" B: "I'm coming, I'm coming. Sheesh, keep your knickers on!"