# The word of Yahweh came to him

"Yahweh gave messages to him" or "Yahweh spoke to Jeremiah"

# Yahweh

This is the name of God that he revealed to his people in the Old Testament.

# in the days of Josiah son of Amon, king of Judah

"when Josiah son of Amon was king of Judah"

# Amon

This is the name of a man.

# his reign

"Josiah's reign"