George Crombie, aged 47, also had a knife stuck in the waistband of his pyjama bottoms during a separate assault.
He told his stepdaughter there would be “murder in this flat” if she told her mother about the abuse, which took place over a three-year period when she was aged between 10 and 13.
Last week, Laura Johnston, now in her 20s, read her victim impact statement to the court, in which she condemned Crombie for “betraying her trust and love in him”.
“How could I ever get over what my stepfather, who I loved and trusted, did to me as a 10-year-old girl?” said Ms Johnston.
The court heard she wished to waive her right to anonymity.
Crombie, with an address in Bloomfield Ave, South Circular Rd, Dublin 8, pleaded guilty at Dublin Circuit Criminal Court to eight counts of sexually assaulting Ms Johnston in their Ringsend home between February 2004 and December 2006.
Yesterday, Judge Melanie Greally said it was clear Crombie was satisfying a particular sexual fetish during the assaults and referred to the use of the dog lead as “extremely frightening” and “degrading”.
She said Ms Johnston had regarded Crombie as her natural father and that as such the “breach of trust was monumental” before she described the abuse as both “unrelenting” and “predictable” occurring every Thursday and Saturday.
Judge Greally said that, having heard the impact statement, it was clear Ms Johnston would continue to struggle with the “premature loss of innocence” and “blight on her childhood that can never be removed”.
She acknowledged that Crombie had made admissions and spared his victim a trial before she imposed concurrent sentences totalling two and half years.
Garda Sandra Fitzgerald agreed with Dean Kelly, prosecuting at last week’s hearing, that Crombie had been with Ms Johnston’s mother since she was a small child and Ms Johnston had younger half-siblings.
The court heard Ms Johnston thought Crombie was her real father until she was 10, when her mother told her he was in fact her stepfather. When told the news, Ms Johnston showed her support for Crombie by ripping up the birth cert that said he was not her real father.
“She indicated she saw [Crombie] as her real father and she had no difficulty with the news she had received,” Mr Kelly said.
However, shortly after finding out Crombie was not her father, he started acting differently towards her, the court heard.
“He started questioning her about her friends and boys,” Mr Kelly said.
Crombie then started going into her bedroom when her mother and siblings were asleep and touching Ms Johnston while she was lying in bed, the court heard. The abuse happened every Thursday and Saturday night, when Crombie had been out drinking.
He entered her bedroom and touched her stomach, legs and bottom while she lay in bed. She believed he had a fetish for stomachs and bottoms, Mr Kelly said.