Etymology of Blasphemy

Here's basic definition of blasphemy:

Blasphemy is irreverence towards religious or holy persons or things. Some countries have laws to punish blasphemy, while others have laws to give recourse to those who are offended by blasphemy. Those laws may discourage blasphemy as a matter of blasphemous libel, vilification of religion, religious insult, or hate speech.

Here's etymology of blasphemy:

The word “blasphemy” came via Middle English “blasfemen” and Old French “blasfemer” and Late Latin “blasphemare” from Greek “βλασφημέω”, from βλάπτω = “I injure” and φήμη = “reputation”. From blasphemare also came Old French “blasmer”, from which English “blame” came.

Blasphemy: ‘from Gk. blasphemia “a speaking ill, impious speech, slander,” from “blasphemein”: “to speak evil of.”'

“In the sense of speaking evil of God this word is found in Ps. 74:18; Isa. 52:5; Rom. 2:24; Rev. 13:1, 6; 16:9, 11, 21. It denotes also any kind of calumny, or evil-speaking, or abuse (1 Kings 21:10; Acts 13:45; 18:6, etc.).”

[etymology of blasphemy https://www.etymonline.com/word/blasphemy]

Here's some selected excerpts from Wikipedia Blasphemy:

Christian theology condemns blasphemy. It is spoken of in Mark 3:29, where blaspheming the Holy Spirit is spoken of as unforgivable — the eternal sin.

Blasphemy has been condemned as a serious, or even the most serious, sin by the major creeds and Church theologians.

• Thomas Aquinas says that “it is clear that blasphemy, which is a sin committed directly against God, is more grave than murder, which is a sin against one's neighbor. … it is called the most grievous sin, for as much as it makes every sin more grievous.”
• The Book of Concord calls blasphemy “the greatest sin that can be outwardly committed”.
• The Baptist Confession of Faith says: “Therefore, to swear vainly or rashly by the glorious and awesome name of God … is sinful, and to be regarded with disgust and detestation. … For by rash, false, and vain oaths, the Lord is provoked and because of them this land mourns.”
• The Heidelberg Catechism answers question 100 about blasphemy by stating that “no sin is greater or provokes God's wrath more than the blaspheming of His Name”.
• The Westminster Larger Catechism explains that “The sins forbidden in the third commandment are, the abuse of it in an ignorant, vain, irreverent, profane … mentioning … by blasphemy … to profane jests, … vain janglings, … to charms or sinful lusts and practices.”
• Calvin found it intolerable “when a person is accused of blasphemy, to lay the blame on the ebullition of passion, as if God were to endure the penalty whenever we are provoked.”

In Britain's last blasphemy execution, 20-year-old Thomas Aikenhead was executed for the crime in 1697. He was prosecuted for denying the veracity of the Old Testament and the legitimacy of Christ's miracles.

Note that a big incident in recent years about blasphemy is that, the Islamic ordered a author killed due to his book. See: Christianity and Islam as Violent Cults.