Is it okay to call someone by their handicap, for instance: Mohamad the blind, Ahmed Alaaraj (the one who limps)...

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

If using such nicknames is meant to mock these people or demean them, then it becomes forbidden and is included in those mentioned in the following verse: Allaah Says (what means): {Woe to every scorner and mocker}[Quran 104:1]

Allaah also Says (what means): {O you who have believed, let not a people ridicule [another] people; perhaps they may be better than them; nor let women ridicule [other] women; perhaps they may be better than them. And do not insult one another and do not call each other by [offensive] nicknames…}[Quran 49:11]

Insulting people is forbidden and those who insult others or mock them are of bad reasoning.

However, if such nicknames are not used as insult or mockery and if the called person is known with that nickname and does not become sad upon hearing it, then this is permissible although we think that it is more appropriate to call people by their real names.

An-Nawawi said: "If the person is known with a given name like the bleary-eyed, or the cripple, or the short, and the like, then it is lawful to refer to him with that, but it is forbidden to mock him with it. If he can be referred to by using other names, then it is more appropriate."

Allaah Knows best.