The story
- Middle Englishmery
- Englishmerry
- Proto-Indo-European*teng-
- Proto-Germanic*þankijaną
- Proto-Germanic*þanhtaz
- Proto-West Germanic*þą̄ht
- Old Englishþōht
- Middle Englishthought
- Englishthought
- English todaymerrythought
From merry + thought, traditionally explained with reference to the pleasant thoughts imagined when the bone is ritually broken.
Etymology from Wiktionary, CC BY-SA 4.0.