The University in Texas called Texas A&M. What does the A&M stand for?

Nothing!
"In 1963, the 58th Legislature of Texas approved of Rudder's changes, and officially renamed the school "Texas A&M University",specifying that the "A" and the "M" were purely symbolic, reflecting the school's past, and no longer stood for "Agricultural and Mechanical."
https://en.wikipedia.org/wiki/Texas_A%26M_University

My father went there right after WWII on the GI Bill and he referred to it as Texas Agriculture and Mining.

'The State of Texas agreed to create a college under the terms of the Morrill Act in November 1866, but actual formation didn't come until the establishment of the Agricultural and Mechanical College of Texas by the Texas state legislature on April 17, 1871.'

'Texas A&M underwent many changes in the 1960s under the presidency of Gen. James Earl Rudder. Under his tenure the college diversified, opening its doors to African-Americans and formally admitting women. Participation in the Corps of Cadets was also made voluntary. In 1963, the Texas state legislature officially renamed the school to Texas A&M University, with the "A" and "M" being a symbolic link to the school's past but no longer officially standing for "Agricultural and Mechanical."'

from the school web site: http://www.tamu.edu/about/history.html