The lerfu shifts (BY1) consist of these cmavo: ga'e, ge'o, je'o, jo'o, lo'a, na'a, ru'o, se'e, to'a.
For past usage, I am searching through the corpus I have collected of 900 kilobytes of pure-Lojban text. The corpus includes all texts published at lojban.org/files/texts, many large texts from the Wiki, and texts from the CVS server such as Alice.
This word is only used in algebra, to mark variables named with capital letters. It occurs one lerfu from the end of a lerfu string, so that it has the same effect as tau.
None of these are used anywhere in the corpus.