How well a thing does what it does, and the act of doing it before others. Both senses are measured by a watcher.
From Old French parfournir (to accomplish fully) with the noun suffix -ance; both how well a thing does what it does and the act of doing it before others are measured by whether it was carried all the way through.
How well a thing does what it does, or the act of doing it in front of others — both senses answerable to whoever is watching.