Origins
Han Chinese Origin
According to a note in Xing Shi Kao Lue citing the Han Shu's Gujin Renbiao, Boyi Liangfu, teacher of the ancient emperor Zhuanxu, may be the source of the Liang surname; the source therefore says that the surname was probably formed from a personal name.
Reference: 亮姓_亮姓的来源和历史_百家姓
Historical Records
Documentary Attestation and Variant Relation
The Zheng Tongzhi's Clan Records includes the Liang surname, which the source says first appeared in the Xingyuan. The source also reports that Liang and Liang-with-the-speech radical are interchangeable and that Liang may in fact be the Liang surname, but this remains a possibility.
Reference: 亮姓_亮姓的来源和历史_百家姓