"That is a genius goal for me," West Ham manager Sam Allardyce said. "You'll struggle to see a better goal than that this season."
The 20-year-old midfielder was offloaded by Manchester United in 2012 after then-manager Alex Ferguson lost patience with his off-field issues.
Allardyce said Ferguson told him that "I hope you can sort him out but if you can he will be a genius," and that "he needs to get away from Manchester and start a new life."
In London, Morrison is thriving.
"The penny's dropped for him ... (with) his lifestyle and his attitude towards everybody and his timekeeping," Allardyce said.
Allardyce's ultra-defensive formation had seen West Ham struggle to threaten Tottenham's goal until Winston Reid stunned the home fans by scoring in the 66th minute.
Then Ricardo Vaz Te fortuitously added another six minutes later, with the ball coming off his knee after Lloris blocked an initial shot.
West Ham's first win at White Hart Lane since 1999 lifted the team to 13th, while Tottenham fell out of the top four to sixth.
"It's a wake-up call that we have to react to," Tottenham manager Andre Villas-Boas said. "We have to bounce back and I trust the team to do that."
There was a heavy police presence inside the ground as part of a crackdown on racism.
In last year's fixture, abuse by West Ham fans put the spotlight back on the anti-Semitism faced by supporters of Tottenham, which has a strong Jewish fan base.
Police threatened to take action against anyone who chanted "Yid," even if it was Tottenham supporters who use the term affectionately to deflect anti-Semitic abuse. But the term, often used as a derogatory term for Jews, was sung with gusto by Tottenham fans and one was arrested at halftime for using it.
The Metropolitan Police said the man was held for causing harassment, alarm or distress.
While Jermain Defoe started in place offseason recruit Roberto Soldado up front, the Tottenham threat was largely coming from Andros Townsend down the right flank. The winger came closest when he cut in and sent a dipping shot just over midway through the first half.
An effort from Gylfi Sigurdsson was easily saved by Jussi Jasskelainen, Paulinho saw a rising shot blaze over the crossbar and also fired over on the volley.
Yet West Ham could have ended the first half in front, with captain Kevin Nolan hooking the ball wide from a free kick.
The breakthrough for West Ham came from Stewart Downing's corner. Reid's header was inadvertently blocked by teammate Nolan next to the line but he immediately sent the rebound into the net.
Mark Noble then played a more intentional role in setting up West Ham's second goal.
Vaz Te latched onto Noble's through ball and after Lloris blocked the initial shot, it ricocheted off his knee into the net. Morrison then completed Tottenham's miserable afternoon with his solo goal.
"Morrison picks the ball up in his own half and heads directly to Vertonghen and Dawson and slips them two like they weren't there, waits for the goalkeeper to go down," Allardyce said. "He has shown how good he is at one-on-ones and how quick he is off the line and he uses his outstanding ability to dink him. ... There is a lot of praise that will come his way and deservedly so after that goal."