Snowball is a small string processing language for creating stemming algorithms for use in Information Retrieval, plus a collection of stemming algorithms implemented using it.
It was originally designed and built by Martin Porter. Martin retired from development in 2014 and Snowball is now maintained as a community project. Martin originally chose the name Snowball as a tribute to SNOBOL, the excellent string handling language from the 1960s. It now also serves as a metaphor for how the project grows by gathering contributions over time.
Stemming maps different forms of the same word to a common "stem" - for example, the English stemmer maps connection, connections, connective, connected, and connecting to connect. So a searching for connected would also find documents which only have the other forms.
This stem form is often a word itself, but this is not always the case as this is not a requirement for text search systems, which are the intended field of use. We also aim to conflate words with the same meaning, rather than all words with a common linguistic root (so awe and awful don't have the same stem), and over-stemming is more problematic than under-stemming so we tend not to stem in cases that are hard to resolve. If you want to always reduce words to a root form and/or get a root form which is itself a word then Snowball's stemming algorithms likely aren't the right answer.
Please address all Snowball-related mail to the snowball-discuss mailing list.
Any such mail sent directly to individual developers may be answered less speedily, and in any case they reserve the right to post their answers on snowball-discuss.