The English word usury is recorded 22 times in the KJV Old Testament. Its New Testament use, found only in Matthew 25:27 and Luke 19:23, comes from the Greek tokos (Strong's Concordance #G5110) which means interest received on money. Interestingly, in the Old Testament, usury is derived from five different Hebrew words!
The most common term translated as usury is neshek (Strong's #H5392). Both it and masha (#H4855 used only in Nehemiah) are defined as any interest paid on a debt. Nashah (#H5383) references a creditor who charges interest while nasha (#5378) refers to the person who borrows from someone extracting the additional money.
The final word translated usury, found four times in Deuteronomy 23:19 - 20, is nashak (Strong's #H5391). Nashak is fascinating in that it literally means, "to bite" or "strike with a sting," alluding to the painfulness of needing to borrow cash. In other Old Testament places it is used to denote the attacking behavior of an adder (Genesis 49:17), fiery serpents (Numbers 21:6) and even the mythical cockatrice (Jeremiah 8:17)!
In the Bible, usury is the charging of ANY interest no matter how small (Exodus 22:25, Leviticus 25:36 - 37, Nehemiah 5:1 - 11). God prohibited the Israelites from charging their fellow citizens interest but allowed them to do so with "strangers" (Gentiles or those not citizens, Deuteronomy 23:19 - 20).
Although interest could not be levied for personal loans among Israelites (to buy food, shelter or clothes, pay taxes, etc.), Scripture did not forbid appropriate interest charged for business (commercial) activities.
In modern times, usury usually means the lending of money at an exorbitant rate or in excess of a legal limit.
Did you know . . .
The First Council of Nicaea, in 325 A.D., forbade the Catholic clergy from charging interest of any amount or kind. The seriousness with which they viewed the profiting from such a practice is reflected in Canon 17 which states, "if after this decree any one (the clergy) be found to receive usury, whether he accomplish it by secret transaction or otherwise . . . he shall be deposed from the clergy and his name stricken from the list."
Jews got involved in banking because, in the middle ages, capital was needed that was not provided by Christians. The reason for this is that the church (Catholics) strictly prohibited charging interest between Christians on pain of excommunication. This left the door open for Jews, who were not under this rule, to lend money with usury without any competition from others (The 1906 Jewish Encyclopedia).
"The consequence of the condemnation of usury by the church was to throw all the dealing in money in the early middle ages into the hands of the Jews" (1911 Encyclopedia Britannica).
The kings of England and France also highly prized Jewish capital since they could (at a later time) demand their interest be returned. Their need was so great that they even required compensation for every Jew who converted to Christianity!
The Westminster Confession of Faith, upheld by Reformed (Calvinistic) Churches, teaches that the charging of usury (any interest) is a sin prohibited by the eighth commandment ("Thou shall not steal," Exodus 20:15).