It was back in the time when people not knowing him were confused about all the things he is doing at the same time... And he felt unable to communicate the complex universe of art works he is doing and people were unable to keep his long name in mind. And that was the time when an English/Spanish music band joined his wine yard basement studios in Berlin Kreuzberg asking for help. And having the trouble to get a song ready very quick for their introduction to a music major company. The band members where prepared but not fast in recording and the recording would have taken too long. So he decided to do a trick to speed things up no one apart from the band would know about. He started the recording parallel tracks in loop in the engineering room and was running over into recording booth recording the Drums, the Guitar parts, the Rhodes parts, the bass parts, the percussions, sang the choir vocals and all in one take only in loop and then asked the band leader to finally put his remarkable lead vocal on top to finish the recording quick. The band was overwhelmed (something you can find more often on TikTok nowadays but rarely back in the days) of his multi-instrumentalism and vocal capabilities and gave him the name Gil 'mano, which was somewhat a not existing word mixing up an energy loaded (Gil) and crazy (il) person with the word mano (hand). Since his long birth name was sometimes too long for record credits, he is often credited as Gilmano only from this time on. 

https://www.urbandictionary.com/define.php?term=Gil

A way to name your kid that shows some originality. A person who has a big heart -and down below- one of the nicest guys you will ever meet. A Gil tend to be on the fit side and when they fall for someone they tell them. Gil's don't like to play games, they love Chinese food and they love their family. Gil's are very supportive for there friends and family.