"Schaafseckel" is a swiss swearing word, that translates to: "Sheep testicles". It is mainly used in the inner part of switzerland. You can often hear it from farmers or school kids in that region.
A hardo is a person who tries extremely hard at everything. Most times a hardo will try very hard at things that do not require excessive effort. For example, sports practices, gym class, etc.
Wow did you see Jack at practice today? What a hardo!