From the article: "I was specifically told by several BP agents that it is the sound of a flashlight hitting a head," Heyman said in a separate email. "I was never told either of those acromyms (or any others). I suspect that those are after-the-fact rationalizations of a disturbing word, but I cannot prove that (I do not directly have evidence). What I do have evidence of is that is was described to me by agents as the sound of a flashlght blow to the head."
This is it, but with a 'K' unless the AZ sector guys use alt spelling.
Josiah Heyman, director of the Center for Inter-American Border Studies at the University of El Paso, thinks the latter definition is more accurate based on what he said Border Patrol officers have told him in the past.
"It comes supposedly from the sound of a person´s head being hit by a flashlight," Heyman wrote in an email. "Their explanation. It is derogatory. Implies people against whom one exercises violent force. That is my interpretation but pretty clear."
Heyman doesn't believe the term "tonc" is an acronym that stands for something else.
Papi me gusto.
!Ai mi cabeza!
Bagster