Let’s try shifting each letter one key right (to reverse):
t → r (t’s left neighbor) h → g m → n y → t l → k So thmyl becomes r g n t k → not English.
t ← y (since y is left of t on QWERTY) h ← g m ← n y ← t l ← k So thmyl = y g n t k → "y g n t k" (no).
Let’s try shifting each letter one key right (to reverse):
t → r (t’s left neighbor) h → g m → n y → t l → k So thmyl becomes r g n t k → not English.
t ← y (since y is left of t on QWERTY) h ← g m ← n y ← t l ← k So thmyl = y g n t k → "y g n t k" (no).