The Hebrew proper name Achaz (אָחָז) is a shortened form of Achaziah, meaning "he has grasped" or "Yahweh has grasped". The most prominent bearer is Ahaz son of Jotham, the twelfth king of Judah, who reigned c. 735–715 BC — one of Judah's most faithless kings.
Ahaz is the inverse of faith. Surrounded by threats — the Syro-Ephraimite coalition seeking to depose him — he refused to trust God and instead sent tribute to the Assyrian king Tiglath-Pileser III, saying "I am your servant and vassal" (2 Kings 16:7). Isaiah's great confrontation with Ahaz (Isaiah 7) is one of Scripture's defining moments: "Ask the LORD your God for a sign." Ahaz piously refused — "I will not put the LORD to the test" — but his piety was actually faithless pragmatism. To this unwilling man, Isaiah announced the Immanuel prophecy (Isaiah 7:14), ultimately fulfilled in Jesus Christ. God's purposes advance despite human unbelief.