Jake and Elwood Blues both have their names tattooed on their fingers, as established in the opening scenes of The Blues Brothers.
Tattoos like these are called knuckle tattoos, even though the actual tattoo is done between the knuckles. Another famous example is "LOVE/HATE" on Reverend Harry Powell's hands in The Night of the Hunter.
Both in-universe and out-of-universe, why do Jake and Elwood have their names tattooed on their hands?
Has anyone involved in the production of the film ever commented on it?