Sammie Szmodics and Liam Delap scored before the break, with the Blues then superbly seeing out victory after Rodrigo Bentancur pulled a goal back in the 69th minute.
Town's first Premier League win in more than 22 years lifts them out of the relegation zone going into the third international break of the campaign.
"I'm not going to shy away from it, it's a really significant moment and a day to cherish in the recent history of the football club," said McKenna.
"Look at the journey the club's been on the last 22 years, the ups and downs, some of the depths, I think for the supporters to see their club win in the Premier League at a fantastic club like Tottenham, against a team like that, in a stadium like this, is a massive day for them.
"For those of us who have been on the journey for the last couple of years it's a really significant day as well. From where the club has come from, competing in the first few Premier League games was a big step, but now of course, making that next step and winning a game, is a really, really significant landmark in the journey.
"As we've said many times, it's a relatively new group coming together, trying to adjust to the demands of the Premier League and, for many, to a new club as well. So it's a really significant step for them.
"We feel there has been some good work going on since pre-season, there have been improvements over the course of the games, have been competitive in lots of the games,, but until you take tat last step and win a game then that's always going to be held over you a little bit. So to do that today, in the manner we did, is a really big day for us."
On Suffolk pop superstar Ed Sheeran coming into the dressing room afterwards, the Blues boss said: "He popped in and congratulated the boys. It was nice to see him. We had his designed (pink third) kit on today, so maybe that brought us a little bit of luck!"
McKenna, who was a youth team player at Spurs and started his coaching journey with them, continued: "I came to this club as a 14 year old, leaving home in Ireland, and I never went back. It's nice to do it here, a club I've got great affinity for, no doubt about that. My father was in the crowd. Lots of people will be very, very proud.
"And it's nice to do it against a really good team. Tottenham are fantastic team playing really, really well at home, there's an amazing atmosphere in the stadium, so that makes it even more special."
On the game itself, he said: "We know for a team in our context, the journey we've been on, coming away from home to a team of this strength, that there were certain elements of the game that would have to be spot on.
"We've built such a brave identity of play that we want to stay true to, but we also know it's a huge step up and we need to be clever in terms of how we're going to compete for points. I thought today our balance of that was really, really good.
"I thought we showed our identity in some moments where we pressed high in the first half, we were aggressive, played with intensity and made it hard for Tottenham to build. There were times we played brave and built out from the back, we scored a goal where we controlled a lot of possession and another terrific goal on the counter attack.
"We managed the game well, we controlled the set plays well. Our organisation and discipline out of possession was terrific and the subs had a good impact. Aro (Muric) made a couple of saves and we were pretty clinical with most of our chances.
"I think we managed the second half well. You know that 2-0 is a really tough scoreline and that they are terrific in the second half of games, especially shooting against that end. You know there's going to be some big momentum, but I thought we managed that pretty well. They've scored a good set play where they worked the block and got the spare man in, but I thought we defended well and always had a threat to get up the pitch. Liam (Delap) kept the centre-halves occupied, Omari (Hutchinson) carried the ball up the pitch, so it never felt like we were completely pinned into our box. It didn't feel like we were getting carved open and they were getting big, big chances.
"They put lots of forwards on the pitch and pushed the game well, but I thought we deserved to get it over the line."
After a two-week international break, Town return to action with a home game against Manchester United. Three of the next four games are at Portman Road.
"We'll have a few days off now and we'll then have a nice long run in to another brilliant game after the break," said McKenna.
"The atmosphere in Portman Road this season has been electric, so I don't know if that can go up too much.
"People can now probably let their shoulders back a little bit in terms of enjoying the season, probably more so the supporters, rather than worrying when the first win would come. For us the process doesn't change."