The story
- Englishyaoi
- Proto-Indo-European*pleh₁-
- Proto-Indo-European*pl̥h₁nós
- Proto-Germanic*fullaz
- English todayyaoiful
From yaoi + -ful, by analogy with yuriful, which is, alternately, a blend of yuri + wonderful.
Etymology from Wiktionary, CC BY-SA 4.0.