As is usual for names ending in יה (-iah), the name Delaiah occurs both with, and without, the final letter ו (waw). We find five different men named Delaiah(u) in the Scriptures:

One of the seven sons of Helioenai, who appear to have been the youngest generation of Solomon’s descendants at the time of the Chronicler’s writing (1 Chronicles 3:24).
The twenty-third of the twenty-four descendants of Aaron to whom King David and the high priest Zadok assigned unspecified duties in the temple (1 Chronicles 24:18; spelled with a final waw).
One of three heads of households whose supposed post-exilic descendants could not prove to be true Israelites (Ezra 2:60 and Nehemiah 7:62). The Jews were sent home with a lot of provisions and it was to be expected that this attracted the attentions of charlatans.
Semaiah’s father, who tried to frighten and discourage Nehemiah (Nehemiah 6:10). Nehemiah assumed that Shemaiah had been hired by Nehemiah’s enemies Tobiah and Sanballat, but he may well have been an embittered son of the previous Delaiah, who perhaps in the absence of his proper papers was confined to his home.
One of King Jehoiakim’s advisors to whom Micaiah transmitted the words of Jeremiah that Baruch had read in Gemariah’s chamber (Jeremiah 36:12). When the scroll of Jeremiah finally ended up in the hands of Jehoiakim, the latter became so irritated by what was written on it that he tore it to pieces and threw them into the fire. Delaiah was one of the three men who pleaded with the king not to burn the words (Jeremiah 36:25). Both occurrences of this name in Jeremiah are written with a final waw.