What is the usage and etymology of phrases such as "Grumpy McGrumpface"

Solution 1:

This Reddit thread has a post which says that it originated with an episode of the Friends TV show. The post (which dates from 2016) says

That convention of nicknaming someone with "Characteristic McCharacteristic" was popularized in an episode of Friends where it was revealed that Ross, a college lecturer, had given all his students nicknames because he didn't know their real ones. After the semester ended he started dating a girl he had named "Cutie McPretty."

The -face part is more recently popularized, but it's been around for years,

I suspect that the Friends script referenced something that was already in current use but even the Friends episode predates "Boaty McBoatface"