The Federal Reserve may be poised to loosen the reins on the economy with interest-rate cuts. But for now, banks are still keeping themselves on a relatively tight leash.

December featured a few notable moves in the market for short-term funding, often referred to as the “plumbing” of the financial system. That included brief jumps in the Secured Overnight Financing Rate, which is a measure of what it costs to borrow cash overnight collateralized by Treasury securities.