Thy is an old-fashioned word for your. It is still used in some churches, for example, "Love Thy Neighbour!"
More specifically in Shakespearean/Elizabethan/King James era English, "thy" is the second person singular possessive pronoun. "Your" in contemporary English, of course, can mean either singular or plural, while in that era "your" would have been used exclusively for the plural. Similarly, the second person singular nominative is "thou" as opposed to the plural "ye." The second person singular objective is "thee" instead of the plural "you." First and third person pronouns remain unchanged.
The King James word "thy" means "your." ("Thy thy" wouldn't mean anything. I assume it's a typo.)
Watch what (not) to say?
It means that beauty comes from within the heart, not from how a person looks.
It means to give up your family and inheritence.
"Love Thy Neighbor" tattoos mean hate your brother before you hate your foe.
It means boxes of stuff
It means a Vietnamese name for a girl.
I pledge my oath to you.
Get out of my face..or leave..or get out of my sight
Follow your instincts.
keep thy faith
Thy Kingdom Come!
Do thy even hoist