Finnish and Estonian are related languages. The word sisu is shared between them. For Finns, sisu is almost a defining feature or aspiration of their national identity. Sisu evokes spirit, resilience, fortitude, commitment, persistence.
The same word, sisu, has a more modest meaning in Estonian. It relates to core content, getting down to the brass tacks of something, a fundamental word in what we, in English, would call a table of contents.
Project Sisu draws on both meanings: grit and resilience; focusing on what matters.