The midfielder completed a move from FC Basel this week.
The Egyptian midfielder completed his protracted move from FC Basel this week, after work permit issues had held up the deal.
He has been brought in to boost a Gunners midfield that has been ravaged by injuries this season with Francis Coquelin and Santi Cazorla both out with long-term injuries.
He is likely to be competition for Francis Coquelin in the Arsenal first team, with them having needed another defensive midfielder for some time.
And Nicholas says he is delighted with the capture of the midfielder, as he is the type of player he has been screaming out for Arsenal to sign.
"Elneny is a perfect fit for Arsenal and someone I've been screaming out for," he told Sky Sports.
"At the start of the season Arsenal needed two positions filling, goalkeeper and a holding midfielder. They signed Petr Cech but never filled the other position, which was a bit of a mistake for me.”
"I'm delighted. He's the perfect age and I'm sure he'll be a fine asset for Arsenal."
The Gunners will now be hoping that Elneny can be a long-term replacement for midfielder Mathieu Flamini.
The Frenchman has stepped up admirably to replace Coquelin this season, but has struggled to bring the same qualities that have made his compatriot such a success in the side.
Indeed, it is expected that Flamini will leave in the summer, according to the Mirror, and the signing of Elneny may have just confirmed that will be happening.