I think it sucks that those short names are considered "emoji". The emoji characters in Unicode are well defined and curated but those short names are not. I look into the latest emoji data and I can't see "smiling imp". That's because the official name for the U+1F608 emoji is "SMILING FACE WITH HORNS".
The origin of those short names is not entirely clear to me but from what I understand, most aliases used in GitHub's gemoji database are extracted from Apple's proprietary Color Emoji font. I don't know how Apple came up with those names and I wish Unicode would start curating a list of official short names for emoji.
@Tody For reference, s9e\TextFormatter's Emoji plugin natively supports the short names defined in gemoji's emoji.json.