Stumbling block

The Koine Greek word,  (Strong's 4625) means either a 'trap-stick' or a 'stumbling block'. In the Bible, skándalon is used figuratively to mean either something that causes people to sin, or something that causes them to lose their faith in Jesus. 

 A trap-stick: a bated stick holding open a trap, tempting prey to touch it, and causing the trap to shut on them . This figuratively refers to a person that entices someone into wrongdoing, getting them to thereby harm or destroy themselves. For example, Peter tempting Christ to refuse the crucifixion. Causing others to sin endangers their connection to God and potentially destroys their souls. If the victim thereby falls into mortal sin, the scandalous deed is considered to be likewise mortal sin.
 A stumbling stone or tripwire: anything that makes someone trip and fall. This figuratively means "something that causes someone to lose faith in Jesus."

Translation

Noun 
As a noun, skandalon means either "temptations that cause people to sin," or "stumbling blocks that cause people to lose faith."

Thus, Matthew 18:7 is translated as either, "Woe to the world for temptations to sin!" or "How terrible for the world that there are things that make people lose their faith!"

Verb 

The verb skandalizō (Strongs 4624) means 'to lead into sin', or 'to cause to fall away from faith.'

Matthew 18:6 is therefore translated as either, "to cause these little ones to sin," or, "to cause one of these little ones to lose faith in me."

Meaning of scandal and scandalise 
Scandal is a "word or act which occasions another's spiritual ruin". Scandalising others is achieved by either enticing them into sin, or by causing them to lose faith.

Scandalising the innocent by the powerful is a mortal sin.

Application to Jesus Christ 
A stumbling stone makes someone trip and fall. This figuratively means 'something that causes someone to lose faith in Jesus.' and in this meaning is applied to Jesus, whose person was so contrary to the expectations of the Jews, that they rejected him and thereby lost their salvation.

Isaiah concludes: "He will be a stone that causes men to stumble, a rock that makes them fall" (Isaiah 8:14). In other words, Jesus is like a stumbling stone because in rejecting him, people fall very heavily.

Bible use

Hebrew Bible 
The origin of the metaphor is the prohibition of putting a stumbling block before the blind (). Geoffrey W. Bromiley calls the image "especially appropriate to a rocky land like Palestine".  In the Hebrew Bible, the term for "stumbling block" is Biblical Hebrew  (). In the Septuagint,  is translated into Koine Greek  (), a word which occurs only in Hellenistic literature, in the sense "snare for an enemy; cause of moral stumbling". In the Septuagint  a stumbling block means anything that leads to sin.

New Testament 
The New Testament usages of , such as , resemble Septuagint usage. It appears 15 times in the New Testament in 12 unique verses according to Strong's Concordance.  These passages are: ,  ,   (3 times),  , , , , , , , , , and .

The noun   has a derived verb,  (formed with the  suffix as English "scandalize"), meaning literally "to trip somebody up" or, idiomatically, "to cause someone to sin." This verb appears 29 times in 27 New Testament verses.

Apart from skandalon the idiom of "stumbling block" has a second synonym in the Greek term proskomma "stumbling." Both words are used together in 1 Peter 2:8; this is a "stone of stumbling" ( λίθος προσκόμματος) and a "rock of offense" ( πέτρα σκανδάλου).  The antonymous adjective  (ἀπρόσκοπος), "without causing anyone to stumble," also occurs three times in the New Testament.

Later use

Judaism 

The Leviticus warning is developed in rabbinical Judaism as lifnei iver "before the blind."

Christianity

Catholicism 
"Scandal" is discussed by Thomas Aquinas in the Summa Theologica. In the 1992 Catechism of the Catholic Church, it is discussed under the fifth commandment (Thou shalt not kill) section "Respect for the Dignity of Persons".

Actively scandalise is performed by a person; to be passively scandalised is the reaction of a person to active scandalisation ("scandal given" or in Latin ), or to acts which, because of the viewer's ignorance, weakness, or malice, are regarded as scandalous ("scandal received" or in Latin ).

In order to qualify as scandalous, the behavior must, in itself, be evil or give the appearance of evil.   To do a good act or an indifferent act, even knowing that it will inspire others to sin — as when a student studies diligently to do well, knowing it will cause envy — is not scandalous.  For example, to ask someone to commit perjury is scandalous, but for a judge to require witnesses to give an oath even when he knows the witness is likely to commit perjury is not scandalous. It does not require that the other person actually commit sin; to be scandalous, it suffices that the act is of a nature to lead someone to sin. Scandal is performed with the intention of inducing someone to sin.  Urging someone to commit a sin is therefore active scandal.  In the case where the person urging the sin is aware of its nature and the person he is urging is ignorant, the sins committed are the fault of the person who urged them. Scandal is also performed when someone performs an evil act, or an act that appears to be evil, knowing that it will lead others into sin.  (In case of an apparently evil act, a sufficient reason for the act despite the faults it will cause negates the scandal.) Scandal may also be incurred when an innocent act may be an occasion of sin to the weak, but such acts should not be foregone if the goods at stake are of importance.

Protestantism 
The term "stumbling block" is common in Protestant writings. An early use was Martin Luther's consideration that the common belief that the Mass was a sacrifice was a "stumbling block."

Scandalised by the State 
One can be scandalised by the State: They are guilty of scandal who establish laws or social structures leading to the decline of morals and the corruption of religious practice, or to "social conditions that, intentionally or not, make Christian conduct and obedience to the Commandments difficult and practically impossible."

Modern "scandal" 

The  Greek word  was borrowed from Greek to Latin to French, and finally to English as "scandal". The modern English meaning of scandal is a development from the religious meaning, via the intermediate sense of "damage to reputation".

Ways to scandalise 

There are nine ways to entice others to sin, persuading them that their sinful conduct is not sinful: 
1) by advice; 2) by command; 3) by consent; 4) by enticement; 5) by flattery; 6) by concealing; 7) by participating; 8) by remaining silent;  9) by defending the ill done.

References

Sources

Citations 

Catholic moral theology
New Testament words and phrases
Book of Leviticus