2015, Kee Lundqvist, "Stories of Significance: The Process and Practices of Sense-Making in the Sherlock Fan Community", thesis submitted to Uppsala University, page 21:
This relatively common crossover/AU is called Potterlock, and the practice of naming particular genre of AU by adding –lock is one unique to the Sherlock fandom on Tumblr: balletlock, Bondlock, tunalock (in which all or some of the characters are, yes, tunas).
2017, Carolina Lindström, "'The power of characterization': A comparative analysis of the transformative works created by the English-language and Japanese-language fandoms of BBC Sherlock", thesis submitted to Stockholm University, page 32:
Balletlock, a portmanteau of the word ballet and Sherlock.