Tank is a nickname from when i played little league. i was about ten years old and a slow runner because i carried some weight with me - nothing horrific, but i wasn't a fast runner.
one day during practice, i hit a grounder threw the hole and got on base. next guy up knocks one into the gap and i start looking like pujols on the bases. one of my teammates yelled out "hurry up, wilson, you run as slow as a tank." well, that's all it took, and everyone - players, coaches, other teams, and even parents started calling me Tank or Tanker. I LOVED that nickname. got called that through the end of 8th grade. i changed from a public school during those years to a private school for my high school years, and the name disappeared. Revived it when i jumped online in the mid-90s and wish i had kept it as part of my life experience beyond 8th grade.