Trying to determine if names like Kohelet or Job (two of which I have yet to hear of anyone being named in the last century) are just rare names or have a reason not be used.
Rabbi Chaim Kanievsky is known for saying (as brought in ויקרא שמו בישראל) that certain "modern" names, such as Shira, are "not real names" and people with such names should have their names changed. Don't ask me how he deals with his own name (which also doesn't appear anywhere in the Torah as a name)! By no means is his 'Psak' universal, however authoritative it may be in its' own right. It is also unclear whether he actually holds this way.EDIT: Here is an excellent article which quoted a number of excerpts from Rabbi Kanievsky on the subject of names, and brings a few other opinions, such as that of Rabbi Moshe Feinstein: http://havolim.blogspot.com/2013/05/modern-names-for-children.html?m=1
The Gemara in Yoma 38b says:
מאי ושם רשעים ירקב? אמר ר' אלעזר רקביבות תעלה בשמותן דלא מסקינן בשמייהו
What is the meaning of ‘But the name of the wicked shall rot’? — R. Eleazar said: Rottenness enters their names, none name their children after them.
Rashi comments: דלא מסקי בשמייהו - לא יקרא אדם לבנו שם אדם רשע, one should not name his son after a wicked person. Tosafot there address some names that seem to be problematic, such as Avshalom. Tosfot Yeshanim there address the name Yishmael.
Regarding the name Iyov, the poskim discuss whether one should name after someone who had bad fortune (ריע מזליה). This affects how to spell names like גדליה/גדליהו, because גדליהו בן אחיקם's life did not come to a happy end. The Rama holds that the name is nevertheless spelled with a ו, and the Beit Shmuel says that is because the Rama is not concerned about naming after people with bad fortune. The Chatam Sofer (Shu"t EH 2:25) says that the Rama would agree that the name Akiva should be spelled with a ה at the end because of what happened to R. Akiva. Perhaps this would be a reason not to use the name איוב.
In the Sefer ויקרא שמו בישראל (by R. Avraham Levi, 2015, p. 115), R. Chaim Kanievsky is quoted as saying that there is no problem naming after Iyov, although it is not common. Zecher David is quoted as saying one should not name after Iyov or Yirmiyahu, because of their bad fortune in life.