Gills boss Mark Stimson told BBC Radio Kent: "I've known him a few years. He scored the winner against us at Yeovil.
"I think he can be a decent player at this level."
He continued: "I watched him in the academy at Charlton. He got the man of the match in that Yeovil game. When he went back from his loan spell we were interested, we put a bid in but were outbid by Southend.
Thankfully no-one stepped in. He's now got to get his head down, and score 20 goals this season Manager Mark Stimson on Simeon Jackson "I've watched his progress. He hasn't played as many games as he would have liked at Southend but an opportunity came up, we'll have a look at him from now until the end of the season and see if he can turn that into a permanent deal.
"He can hold the ball up, he's strong, he's got good physical strength. If he can get in the team, be loved and wanted then I'm sure he'll do well for us."
Twelve-goal top scorer Simeon Jackson remains at Gillingham despite speculation he would leave for a bigger club.
Stimson said: "Thankfully no-one stepped in. He's now got to get his head down, and score 20 goals this season. If you'd have handed us that at the start of the season we would have grabbed that."
Unsettled striker Mark McCammon turned down the chance to move to league one Carlisle United, and both Hereford and Barnet enquired about signing Gillingham defender Garry Richards, but an eye injury is preventing Richards from training at the moment so the deal fell through.