Isaiah in Fausset's Bible Dictionary

Yeshayahu or Isaiahuw (?), Hebrew "the salvation of Jehovah," his favorite expression, which means the same as the name "Jesus", who is the grand subject of his prophecies, and in whom in the New Testament the name Jehovah merges, being never found in Scripture after the Old Testament. The Yahu (or Jahu) in Yeshayahu shows that Yahweh (or Jahveh) is the more correct form than Jehovah. Son of Amoz (not Amos), a younger contemporary of Jonah, Amos, and Hosea in Israel, and of Micah in Judah. His call to the full exercise of the prophetic office (Isaiah 6:1) was in the same year that king Uzziah died, probably before his death, 754 B.C., the time of the building of Rome, Judah's destined scourge, whose kingdom was to stretch on to the Messianic times which form the grand subject of Isaiah's prophecies. Whatever prophecies were delivered by Isaiah previously were oral, and not recorded because not designed for all ages. (1) Isaiah 1-6, are all that were written for the church universal of the prophecies of the first 20 years of his ministry. New epochs in the relations of the church to the world were fittingly marked by revelations to and through prophets. God had given Judah abundant prosperity during Uzziah's reign of 52 years, that His goodness might lead the people to loving obedience, just as in northern Israel He had restored prosperity daring the brilliant reign of Jeroboam II with the same gracious design. Israel was only hardened in pride by prosperity, so was soon given over to ruin. Isaiah comes forward at this point to warn Judah of a like danger. Moreover, in the reigns of Ahaz and Hezekiah Israel and Judah came into conflict with the Asiatic empires. (See AHAZ; HEZEKIAH.) The prophets were now needed to interpret Jehovah's dealings, that the people might recognize His righteous judgments as well as His merciful longsuffering...

Link: https://bible-history.com/faussets/I/Isaiah/