To safeguard something is to guard, protect, or secure it. Often this term suggests taking forceful measures to ensure something does or does not happen. As a result, the term conveys a degree of assurance that the safety of something is guaranteed. Safeguard is more likely to be used of ideas or concepts—immaterial things—than it is of property or physical objects. For instance, you’re more likely to hear of a leader or governing body taking measures to safeguard the rights of a specific group than to safeguard a wetland, the latter being better suited for use with the verb protect.
To corroborate something is to make more certain of it with evidence. In a courtroom, witnesses might be called to corroborate a story put forth by a defendant. Early findings in scientific research might be corroborated by additional scholarly work or laboratory results. More broadly, corroborate means “to strengthen”—and since this term's debut in English in the first half of the 16th century, it has been used to refer to strengthening or reinforcing things materially, to strengthening the health of things or people, and to strengthening a claim or statement.
The noun brainchild is used to refer to a product of one’s creative work or thought (the child of one’s brain, of course!). This heady compound is used of events, campaigns, companies, or elaborate projects—or the animating idea behind them. Use of this term usually connotes a degree of admiration for something truly original, and is almost always used in the context of giving credit or attributing success to a certain creative individual. So where there is a brainchild, there is usually a "brain parent" mentioned nearby.