Coming from the word Hamstring. Hamstringed is the past tense of being Hamstrung. IE, to be slowed down by act of receiving hamstring. Once you are Hamstringed, your movement is slowed by up to 50%. This effect will usually last for about 45 seconds. During this time, you are more likely to get owned, pwnd, and/or phwned by someone who is not hamstrung, thus give them the advantage to move at default speed.
Person A: Hey, come over here before we get caught.
Person B: Ok, OMW
Person A: Oh no!!
Person B: What's wrong?
Person A: Oh shit!, I’m hamstringed son!!
Person B: Well, come over here, we can hide
Person A: I’m hamstringed!!
Person B: ???
Person A: I’M HAMSTRINGED!!
Person A: Hamstringed
Person B: ...