When you're a child, you know you're really in trouble when you hear your mother using both your first and middle names. Even if you don't know what you did, you might as well just start apologizing, because Mom is mad, and she's not going to let you off easily.
I first started using Samantha's middle name when she was around two. I find I use it mostly when I know she knows better. Dumping her snack onto the couch, spilling her juice at breakfast because she's wiggling around in her chair too much, or getting her clothes soaked when she was supposed to be just washing her hands, will all elicit a "Samantha Keiko!" from me.
The kids learn pretty fast the extra significance to the two names usage, too. Whenever I use it, Sammy always stops what she's doing and turns toward me, hands clasped behind her back, head down, looking through her bangs with sheepish eyes.
I didn't realize quite how fast they pick up on the nuance until I started hearing Ella use Keiko. She really can't say Sammy yet, so she generally doesn't address her sister by name. But when she's mad because Samantha took a toy from her, or isn't sharing, or when she sees Samantha do something she knows she shouldn't be doing, I'll hear, "Keiko!" come out of her mouth. It makes me smile every time.
This morning, Ella dumped her cereal bowl full of milk on the table on top of her peanut butter toast after smearing the toast face down on the table while I was helping Sammy go to the potty. When I got back into the kitchen, I scolded her, and for the first time, used her middle name.
"Ella Kameko!" I said.
"Keiko," she corrected.