Thanks! We get a lot of volunteer plants - sometimes it's a happy accident and sometimes it's just weeds - and I wasn't sure which this was. I certainly don't want them to crowd out the intentionally-planted flowers!
I don't for a fact. Relying on probability and context clues. Someone posting the question in English and using the word yard instead of garden to describe a lawn of grass isn't from this range:
https://en.m.wikipedia.org/wiki/Ornithogalum_umbellatum