The meaning of «أليم» is "one who causes pain," just as «مؤلم» is. «أليم» is on the pattern of «فعيل» , meaning «مفعل» (which is rarely used in the Arabic language).

Narrated Abu Wail: `Abdullah bin Masud said, "Allah's Messenger said, 'Whoever takes an oath when asked to do so, in which he may deprive a Muslim of his property unlawfully, will meet Allah Who will be angry with him.' So Allah revealed in confirmation of this statement:--"Verily! Those who Purchase a small gain at the cost of Allah's Covenant and oaths, they shall have no portion in the Hereafter..." (3.77) Then entered Al-Ash'ath bin Qais and said, "What is Abu `Abdur-Rahman narrating to you?" We replied, 'So-and-so." Al-Ash'ath said, "This Verse was revealed in my connection. I had a well in the land of my cousin (and he denied my, possessing it). On that the Prophet said to me, 'Either you bring forward a proof or he (i.e. your cousin) takes an oath (to confirm his claim)' I said, 'I am sure he would take a (false) oath, O Allah's Messenger .' He said, 'If somebody takes an oath when asked to do so through which he may deprive a Muslim of his property (unlawfully) and he is a liar in his oath, he will meet Allah Who will be angry with him.' "