Many interpreters understand anathema and anathemasimply as different spellings of the same word that may be used interchangeably. If that were true, there would be no point in including these words in a book of synonyms. Like heurema and heurema and epithema and epithema, anathema and anathema probably were once no more than different pronunciations of the same word that eventually came to be spelled in two different ways. And in such cases it is not unusual for words with slightly different spellings to develop different meanings and so to become independent. For example, one member in each of the following pairs of words began as a variant spelling of the other: the Greek thrasos and tharsos, the Latin Thrax (Thracian) and threx (a gladiator), the German rechtlich (just) and redlich (upright), the French harnais (armor) and harnois (harness), and the English frayand frey, allay and alloy, and mettleand metal.Anathema and anathema share that same type of derivation.
Earnest debate about the different meanings of anathema and anathema occurred even among the early Hellenists. Salmasius, for example, was among those who argued that the words had distinct meanings, at least as they were used in Hellenistic Greek; Beza was among those who denied such a distinction. Perhaps the truth lies somewhere in between, though nearer to one side than to the other. After weighing all the evidence, the most reasonable conclusion is that anathema and anathema have distinct meanings that were recognized and observed by many but not by all.
In classical Greek anathema is the predominant form and the only one that Attic writers permitted. It was the technical word for costly offerings that were presented to the gods and then suspended or otherwise displayed in their temples. These offerings were separated from all common and profane uses and were openly dedicated to the honor of the deity to whom they were originally presented.
When the Hebrew Scriptures were translated into Greek, however, a new meaning was needed for anathema, because the Scriptures spoke of two ways in which objects might be holy, that is, set apart for God and devoted to him. The children of Israel were devoted to God, and he was glorified inthem; the wicked Canaanites were devoted to God, and he was glorified onthem. Persons and things might be heremthey might be devoted to God for good or for evil. There was such a thing as being "accursed to the Lord." Part of the spoil of a city might be consecrated to the Lord in his treasury and a part utterly destroyed, though each part was dedicated to him. These distinct concepts were expressed by using anathema and anathema. Those who believe that separation from God is the central idea of anathema are not able to trace a common meaning between it and anathema, which plainly refers to separation to God, or to show the point at which these words diverge. Those who believe that separation to God is implied in both cases face no such difficulty.
In the Septuagint and Apocrypha anathema and anathemawere used in distinct ways. Because of the variety of readings in the various editions, however, it is difficult to determine if the distinction between them was universally observed or to know how consistently the distinction between them was observed. In Tischendorf's critical edition of the Septuagint (Strong's #1850), however, the distinction between the two words is maintained in many passages, though that is not the case in some earlier editions of the Septuagint. In the New Testament anathema is always used to express the sacrum (sacred thing) that is pleasing to God, while anathema is used to refer to things that deserve God's wrath. These words are not used frequently enough in the New Testament, however, to convince an opponent of this view. Anathema occurs only once: "Then, as some spoke of the temple, how it was adorned with beautiful stones and donations [anathemasi]"( Luke 21:5). Anathema occurs no more than six times ( Acts 23:14; Romans 9:3; 1 Corinthians 12:3; 1 Corinthians 16:22; Galatians 1:8-9), and its use in these passages confirms the distinction made above.
Some of the Greek fathers neglected this distinction. Others, however, observed it implicitly, and some explicitly recognized the distinction and accurately and precisely traced its development.
Let us summarize our findings. Based on similar phenomena in all languages, it is probable that anathema and anathema gradually developed distinct meanings. In Scripture the two ways that persons and things may be dedicated to Godfor good or for evilare described by using these two slightly different forms of the same word. Every New Testament use of these words maintains this distinction. The later ecclesiastical books also maintain this distinction, though not perfectly. I conclude, therefore, that the sacred writers of the New Testament deliberately used anathema and anathema in different senses. Luke used anathema ( Luke 21:5) because he intended to express that which was dedicated to God for its own honor as well as for God's glory. Paul used anathema in the sense of that which is devoted to God's honor (as were the Canaanites of old) but to its own destruction. And in the end, every intelligent being who is capable of knowing and loving God and who has been called to this knowledge must be either anathema or anathema to him. acceptable and consecrated to himself or as detestable to him and his wrath and as owed and subject to punishment."
Trench, Richard C. Entry for 'Gift'. Synonyms of the New Testament. https://www.studylight.org/lexicons/trench/34. 1854.