The 22-year-old midfielder has joined on loan from Bournemouth and could face Hearts on Saturday.
"I'm really looking forward to the challenge," he told the Saints website.
"I've spoken to a couple of the lads from down south who have played up here and they said it'll be a great experience for me and that they really enjoyed it. Hopefully I can come here and make the most of it."
Butcher added: "I will hopefully add lots of energy to the midfield and I like getting up and down the pitch.
"I'm always looking to get on the ball and to make things happen."
Saints have also signed 20-year-old winger Isaiah Jones on loan from Middlesbrough but he will arrive next week.
Meanwhile, striker Callum Hendry has extended his contract until the summer of 2022.
Hendry said: "I've been wanting to get it over the line for a while now but these things take a while. I'm really enjoying my football at the moment and I'm excited about my future at the club.
"Hopefully now I can get myself a run of games and try to nail down my starting place. I want to be the first name on the manager's team sheet and obviously I want to score plenty goals."