The incident happened in the small city of St. Pölten in Lower Austria, when the 21-year-old woman asked the tattooist if he could draw the symbol on her.
A court heard that he gladly obliged and carefully drew a template for the correct symbol, showing her a picture to confirm it.
When it came to applying the ink, however, he deviated from the original design and added the phallic drawing and swear word instead.
The victim only realised when she went home and looked at her new tattoo in the mirror.
When asked by the judge why he had done that, the hobby tattooist, also aged 21, replied: “Just because.”
In addition to causing bodily harm, the defendant - who had only been released from prison in May last year - also faced several other charges relating to burglary and fighting.
He was sentenced in total to three-and-a-half years in jail and will be held in an institution for mentally abnormal offenders. The sentence is not yet legally binding.