Sui generis
Sui generis (; ) is a Latin phrase that means "of its (his, her, their) own kind; in a class by itself; unique."
Sincerity
According to the American Heritage Dictionary, the Latin word "sincerus" is derived from the Indo-European root "*sm̥kēros", itself derived from the zero-grade of "*sem" ("one") and the suffixed, lengthened e-grade of "*ker" ("grow"), generating the underlying meaning "of one growth", hence "pure, clean."