For Anneliese's middle name, we just chose a name we liked. Her first name is after DH's grandmothers (Anne and Elsie), so we felt like we could just choose something we loved the sound of for her mn. We wanted it to be cute, quirky, and old-fashioned. We chose Olive and love it.
For Hazel's middle name, we wanted a name with significance because her first name was just a name we liked (not after family or anything). We chose Dianna after my grandma, who we are very close with- she's like a second mother to me (more of a first mother these days, now that I think about it). It didn't cause any hurt feelings that I'm aware of because it's known how close we are with her.
For this new baby, we chose Luna as a name we just liked with no family history. We couldn't find another name in our family we liked well enough to use as a middle name, so we decided to use an Irish name instead, kind of in honor of DH's family's Irish heritage. We chose Mairéad because we love how it sounds.