“对上帝或神圣事物的不敬或亵渎性言论”，最早出现在13世纪，源自古法语 blasfemie（“亵渎”），进一步追溯到晚期拉丁语 blasphemia，再往前是希腊语 blasphēmia，意为“恶言中伤、不敬的言辞、诽谤”，其动词形式 blasphēmein 则意为“说坏话”。
这个词的第二部分 phēmē 意为“言辞”（来自原始印欧语词根 *bha- (2)，意为“说、讲、表达”）。而第一部分的来源尚不明确，可能与 blaptikos（“有害的”）相关，但也有人提出与 blax（“懒散的（身心）、愚蠢的”）相联系；德·范则建议它可能源自拉丁语 malus（“坏的、令人不快的”），而该词又来自原始印欧语词根 *mel- (3)。在《旧约》中，这个词更具体地指向一种罪行，即对耶和华作为犹太人统治者的亵渎，类似于叛国罪。
Blasphemy cognizable by common law is described by Blackstone to be "denying the being or providence of God, contumelious reproaches of our Saviour Christ, profane scoffing at the Holy Scripture, or exposing it to contempt or ridicule"; by Kent as "maliciously reviling God or religion"; and by Chief Justice Lemuel Shaw as "speaking evil of the Deity with an impious purpose to derogate from the Divine Majesty and to alienate the minds of others from the love and reverence of God." [Century Dictionary, 1895]
布莱克斯通描述的普通法下可认定的亵渎罪是“否认上帝的存在或其天意，蔑视基督的言辞，亵渎圣经，或将其置于轻蔑或嘲笑之中”；肯特则称其为“恶意侮辱上帝或宗教”；首席法官勒梅尔·肖则认为，亵渎是“出于不敬的目的，恶意中伤上帝，以贬低神圣的威严，试图使他人远离对上帝的爱与敬畏。” [《世纪词典》，1895年]
To laugh at the pretensions of Mohammed in Constantinople is blasphemy. To say in St Petersburg that Mohammed was a prophet of God is also blasphemy. There was a time when to acknowledge the divinity of Christ in Jerusalem was blasphemy. To deny his divinity is now blasphemy in New York. Blasphemy is to a considerable extent a geographical question. [Robert G. Ingersoll, quoted in "Discussions," 1902]
在君士坦丁堡嘲笑穆罕默德的自称就是亵渎。在圣彼得堡说穆罕默德是上帝的先知也是亵渎。曾几何时，在耶路撒冷承认基督的神性被视为亵渎。而在纽约，否认基督的神性如今被视为亵渎。亵渎在很大程度上是一个地理问题。[罗伯特·G·英格索尔，摘自《讨论》，1902年]
