A technical is a recentism for a light improvised fighting vehicle, typically an open-backed civilian pickup truck or four-wheel drive vehicle mounting a machine gun, anti-aircraft gun, anti-tank weapon, or other support weapon, somewhat like a light military gun truck
The term technical describing such a vehicle originated in Somalia in the early 1990s. Barred from bringing in private security, non-governmental organizations hired local gunmen to protect their personnel, using money defined as “technical assistance grants”. Eventually the term broadened to include any vehicle carrying armed men. Technicals have also been referred to as battlewagons, gunwagons, or gunships.
Additional Information: https://en.wikipedia.org/wiki/Technical_(vehicle)