This phrase was coined by Shakespeare, in Hamlet, 1603. It is a simple allusion to a path scattered with flowers. phrase is used when Ophelia is warning her brother take his own advice and not reject the difficult path of righteousness that leads to Heaven in favor of the easy path of sin.
The pleasant route through life, of pleasure and dissipation
primrose-path. Dictionary.com. Collins English Dictionary - Complete & Unabridged 10th Edition. HarperCollins Publishers.