The important noun δικη (dike) initially meant manner or custom and came to denote established protocol and finally became a legal term covering that what is just or right, and the penal (just) consequence of violating a rule. This word comes from the same Proto-Indo-European root "deyk-", to show or point out, as the verb δεικνυμι (deiknumi), to show or point out, and the familiar noun δακτυλος (daktulos), finger (to point with).

In the Bible our noun δικη (dike) occurs a mere 4 times; see full concordance, mostly in the sense of just consequence, and once as the more general concept of justice (Acts 28:4), although this occurrence may also be an appellation of the goddess Dike (= Justice; see the link below).

It needs to be remembered, however, that the concept of justice today differs from that of Biblical times. In our times, justice refers to the application of previously established laws, and it doesn't matter whether these laws are "fair" or not. Laws are drawn out of a hat by the Supreme Court, which is mostly concerned with maintaining the status quo of the ruling elite (which, conveniently, appoints the Supreme Court). The local courts where we ordinary slobs end up don't look at what is fair or ethically virtuous but merely whether the accused has actually violated the rule for which he or she is tried. That is why in our time, one is "guilty" when one has been found in breach of any previously established law, not when one has actually done something wrong.

In the old world, people still had a sense of absolute justice. And that absolute justice was considered either divine (by pagan systems) or integrated in created nature (as the Hebrews figured): the software upon which humanity was designed to operate. A wholly just society was expected to run without a hitch: individuals would be wholly free to follow their own inclinations, wholly voluntarily subjecting themselves to the rules everybody agreed on (Jeremiah 31:33, Romans 2:15).

An example of this kind of software is language. Nobody has to be forced into learning the words we all agree on because voluntarily following the rules of language allows people to be much more efficient and thus happier. Ultimately, when everybody understands what justice is, humanity will form a "city" like bees form a beehive. That city is called the City of God (Psalm 46:4, 87:3) or the New Jerusalem (Revelation 3:12, 21:2).

A violation of a just (that is: divine or natural) rule would bring about unhealthy people and an unstable society, simply by natural consequence. A human court was established to prevent dire consequences by punishing evildoers before nature could. And that's initially where the human justice system came from. But the Lord's final judgment, as it is so generously called, is a natural consequence of the way one leads one's life, not some kind of court room with a lot of biased people explaining things. Just like you get sick when you don't eat your vitamins, so you'll go to eternal destruction when you don't embrace the Lord of Life (2 Thessalonians 1:9).

The Biblical idea of being just and righteous should be understood along those same lines: not as being compliant to some abstract legal system but to the natural laws upon which mankind was designed to operate, and upon which mankind must learn to operate. Being righteous has to do with rightness: with being correct in a very scientific way: if you are right, then it will work; if you are wrong, then it won't work (Deuteronomy 18:22, 1 Kings 18:24). God's final judgment may come as a shocker to the unjust and ignorant (Hosea 4:6) but the righteous know perfectly well what's coming and don't fear it a bit.

The noun δικτυον (diktuon) means net (what a fisherman uses), and its similarity to the previous is remarkable, albeit probably accidental (albeit not useless to creative enough poets; also see the noun λινον, linon, thread). It's thought to stem from the unused verb δρεπω (drepo), to collect (fruit), which is remarkable as well since the Hebrew word for fish, namely דג (dag), stems from the verb דגה (daga), to be multitudinous, from which also appears to have come the noun דגן (dagan), meaning grain or cereal.

When Jesus told his disciples-to-be that he would make them fishers of men (Matthew 4:19), he didn't mean that they would catch men against their will, and roast and eat them. Paul wrote that it's for freedom that Christ has set us free (Galatians 5:1) and the word he uses is the aforementioned noun ελευθερια (eleutheria), or freedom-by-law: the kind of freedom that comes from the mastery of the rules that govern the game (the freedom to say whatever is on one's mind comes from the mastery of the rules of language; the freedom to jam away with friends comes from the mastery of the rules of music; the freedom of a perfect society comes from the mastery of the rules that govern society).

In that regard, the nets with which the disciples catch men and render them the freedom of Christ, represent the law to which men willingly submit, as well as the love that fulfills all law (Romans 13:8). Note that half the occurrences of our word tells of nets that have broken, need mending or washing. It's used 12 times; see full concordance.