[Izkata]

> has anyone even been legally named Discord before?

There was a Roman goddess named Discordia (where "discord" came from), and in the 90s Hercules and Xena TV series the Greek goddess used that Roman name instead of Eris, but simplified to just Discord.

Those two series were pretty popular, so I can see it being more likely recently than in that 1950s census sibling comment found. On the flipside, that character is probably not something parents would want for their daughter.