The backgrounds usually are too vague to fit any character: They use labels like "Noble" "Criminal" "Charlatan" "entertainer" "hermit" "sage" "Acolyte" etc
If a githz is a noble does not have to mean he´s a noble from baldur´s gate, that could simply mean that he´s from the upper military caste of the Githzyanki instead of one the g'lathk.
If he/she was an entertainer that could mean he/she was a gladiator or a dragon rider in the gith society.
If he/she was a criminal he could mean he simply have a friend on the githzerai, worship a god or have a flumph pet (or at least he does not kill them on sight. BTW. What the blue blazes, githzs!!! Who does not like
Flumphs ?) . That would be "crimes" in githyanki society.
If he was an acolyte, since there´s no formal religion for the githyanki they could be one of the knights of the lich queen Vlaakith.
If he was a salilor that meant he could be a former crew of a spelljammer or one of the Far Travelers.
etc etc
