The 21-year-old 6ft 2ins midfielder came through the ranks at Southend United before joining the Posh on a four-year deal for an initial fee of £200,000 in August 2012, which could rise to £500,000.
Capped at Republic of Ireland U18, U19 and U21 level, Ferdinand has scored 11 times in 112 games and will give Town another great option in the middle, with midfielder Jonathan Smith out for the rest of the season with a double leg break, Andy Parry and Solomon Taiwo just back in training and on-loan West Ham United starlet Pelly Ruddock Mpanzu having returned to the Hammers.
Ferdinand scored 10 times in 71 games at the Shrimpers between 2010-12 and once in 36 appearances since joining Peterborough.
He joined League Two Northampton Town for a month at the end of October, playing five times before being recalled by Posh.
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