DS1 was because we tried a bunch of names, but they either sounded strange with his surname, or they just didn't fit him. The only thing my ex and I had agreed on beforehand was that he wouldn't get a unisex name...and then a unisex name was the one that fit. We just kept looking at him and thinking, "yeah - that's his name".
DD1...I'd waited a long time for a second baby (several years of never explained secondary infertility, followed by a series of three miscarriages). DH had his heart set on the name "Emma' for a girl. I didn't really care for it, but when she arrived, and turned out to be a girl, I was so glad to have a real, live baby again that I gave in on it.
DS2...dh and I found it really, really hard to agree on a boy's name. We have completely different tastes. So, we eventually each short-listed to 10 names, and ds2's name was the only one that appeared on both lists (I beileve it was in 10th place on both!).
I honestly don't remember how we settled on dd2's name. We just liked the sound of it.
I have a thing about two syllable names. I won't choose names that are any other length. So, my children have a total of eight names between them (not counting surnames - but, oddly enough, my maiden name, first married surname and current surname are all two syllables, as well), and all eight are two syllables. The initial vowel sound in each of my children's names is also a short "e" sound, but that was an accident.
I was named (middle name) after my late maternal grandmother, and I hated her guts, and spent much of my life hiding the name from everybody I could hide it from. So, I don't do names in honour of anybody. None of my chlidren's names (first or middle) honour anyone I know.