Paroled killer Edward “Butchie” Corliss drunkenly confessed to gunning down a Jamaica Plain convenience store clerk in 2009, his younger brother testified yesterday, but William “Billy” Corliss claimed he was so terrified of a reputed crime family’s disdain for “snitching” that he kept quiet for months. “For years, I was associated with the Winter Hill Gang,” East Somerville native William Corliss, 64, said in Suffolk Superior Court, where his brother Edward is facing murder charges. “I know they don’t take lightly to somebody trying to testify.” William Corliss’ alleged underworld ties surfaced in the sixth day of Edward Corliss’ murder trial for the cold-blooded killing of Surendra Dangol, a 39-year-old Nepalese immigrant, in a Jamaica Plain Tedeschi’s on Dec. 26, 2009. Edward Corliss, 65, was on parole from a life sentence for killing a Salisbury store clerk in 1971. Hours after Dangol was killed and $746 was stolen from the register, Edward Corliss showed up at his brother’s house with a six-pack of beer and a wad of cash, William Corliss said. “He was pulling it out of his pockets, laughing, throwing it in the air, like he hit the jackpot,” he said. “I asked him where he got it. He said, ‘I pulled a score. . . . The guy said there was no money, but I found it. He lied to me, and I shot him.’ ” When Boston police questioned William Corliss about the crime, he denied knowing anything, he testified, staying silent as police drove him through the city. “It’s all organized crime,” William Corliss said. “Charlestown, Somerville, East Boston, South Boston, and I was getting driven around in an unmarked cruiser. I was terrified someone would see me.” But when he was called before a grand jury, William Corliss said he told what he knew. “I didn’t want to perjure myself,” he said.