Short for t-sip, teasip, a term that many Aggies use to refer to the longhorns.
It was a term coined by Aggies many years ago as while they were off fighting in the war, the longhorns were sitting at home sipping tea. Other things as well but yeah; I either call texas university students sips or horns; this conversation has just happened to be sips.
I don't really use it as a derogatory term as others do, as obviously I have no real relation to those wars being fought many years ago. Simply my fish camp counselor used it the whole week while I was attending camp and it kind of stuck.