The word "rub" in the context of Shakespeare's work and the time is synonymous with "problem" or "issue," so what it meant was - that is the source of the problem, or this is where the issue lies.
"Therein lies the rub" means that a difficulty or obstacle is present in a situation. It refers to a problem that complicates or hinders progress in a particular endeavor.
"Therein lies the rub" indicates that you have identified the root cause of the irritation. "That's what really ticks me off" is another way of putting it.
He never returned to his home-town, and therein lies a mystery.
Excalibur's sheath was said to have magical abilities that no harm would befall he who wore it. Therein lies the rub, Arthur lost or forgot the original sheath and thereby went on to his doom.
Therein
The answer lies in the question. your required word is "seven letter", as it contains eleven letters.
Therein lies the problem with STD infections; you don't know for sure if the person is infected.
Platypuses neither eat corndogs, nor are they kept as pets. Therein lies your problem.
pleural rub
white lies mean small lies<3
Yemen
Literature unlocks the imagination and therein lies the ability to percieve the beauty and color that is life.
Check your local ordinances on livestock and therein lies your answer. Keep in mind that most municipalities will not allow it.
"To rub one out", it means to masturbate.