One must read Paul's letters very carefully.

Paul often writes using puns and play on words.

What is not said can be as important as what is said.

Paul uses many Greek words that have specific meanings in Greek philosophy, history and/or culture to his Greek audience.

Main purpose: Call the leadership (bishops) to task for taking the church in directions not in line with Christ. Surprisingly, there is little if any mention of the modern English sense of "joy".

This Greek word for "opinion" was chosen in the LXX (Septuagint) to represent the Hebrew word for "glory" . This religious meaning continues to this day.

The ancient Greek word "δόξα" ≈ "expectation, opinion" and went to "appearance" to a narrowing of "good repute" to "honor" to (Latin) "glory".

• The "glory" of the Lord is the "opinion" of the Lord.
• Giving "glory" to God is deferring to the "opinion" to God.
• Your own "glory" is your own "opinion" and/or "appearance".

This Greek word is part of the word "doxology" and of the word "paradox" as something that goes beyond opinion or appearance (in a strange way).

The Greek word for "glory" is a narrowing of the ancient Greek «δοκειν» which has to do with thinking well of something or someone as in an expectation.

More: Converse fallacy: If A then B does not mean If B then A

More: Expectation of a glorious Greek opinion on a doxology

The Greek word often translated as "joy" can be mistaken as meaning "merry" or "great happiness" or "bliss". The word "joy" comes, through French, from the Latin "gaudia" ≈ "joy" and which became "gaudy".
The ancient Greek word "χαρά" ≈ "favor, grace" was the word used to translate the Hebrew word. Following Jesus is not all "joy" in the modern English sense of the word.
At the time, the meaning of "suffer" was to "passively endure". So much of this endurance was painful persecution that the word took on the meaning it has today. Another Greek word meant "suffer" as in "to allow".

More: A joyous thank you for the grace of a gaudy favor