Wingman is a role that a person may take when a friend needs support with approaching potential partners. It came from the movie Top Gun. A wingman is someone who is on the "inside" and is used to help someone with intimate relationships. In general, one person's wingman will help him or her avoid attention from undesirable prospective partners or attract desirable ones, or both.
The "pre-wing" refers to the talking up of one friend to another in order to build an attractive persona before any direct interactions. The pre-wing is then usually followed by the wingman role. After the wingman role has been executed successfully, the one getting the lady then goes into foreplay with the lady and has sex with her.
Though some think the term originated in sports (i.e. from a "wing" or "winger" in association football/soccer), it actually originated in combat aviation in various international military aviation communities shortly before and after the advent of fighter jets. Pilots flying in formation, especially when in combat training or in actual aerial combat, refer to the pilot immediately next to them (traditionally on their right, sometimes on either side) as their "wingman" (i.e. the man on their wing). In actual aerial combat pilots are often trained to attack and defend in pairs watching out for each other, thereby making the term even more clearly demonstrated. The term is also very commonly used in combat aviation on longer range aviation patrols which are often carried out by only two fighter planes, sometimes manned by only two pilots depending on the type of aircraft. On these two plane patrols (Air Force) or "watches" (Naval Aviators flying protective patterns around surface vessels on timed intervals) referring to the pilot that an aviator is teamed with on patrol as their "wingman" is very common.