Apparently I am one of the few people who did not know “o’clock” is the contraction for the phrase “of the clock.” The explanation is listed on several sites, including Answers.com.

Matt Ball on Words@Random has a fascinating description of the origin of this word. It is used today to describe someone who is doesn’t pay debts, is lazy, or both. The verb “beat” in the 1800s meant “to swindle or cheat.” Deadbeat was used in military slang in the Civil War to describe a soldier who shirked duty, especially by faking injury or illness. I believe the most common usage today goes to those who don’t meet their financial obligations, such as “deadbeat dads.”

Wikipedia says the word is a declaration of affirmation meaning “So be it; truly.” It is found in the Hebrew Bible and the New Testament, and is a concluding word for prayers and hymns. Simplybible.com says when it is used at “…the end of a prayer it expresses the genuineness or truth of the petition or praise. Amen means ‘truly’ or ‘fair dinkum’.” It also is used colloquially to express strong agreement, as in “amen to that.”

The Phrase Finder says the meaning is “Honest and straightforward, especially of business dealings.” The origin is also straightforward, since “square” meant “fair and honest” in the 16^th century. The expression is therefore tautological, which means to use different words that mean the same.

Everyday Mysteries has an extensive and interesting discussion about possible origins of this expression. It mentions that an often quoted incorrect source was that the animals would huddle in thatched roofs during storms and be washed out. The roofs were water resistant and sloped to allow water to run off. The animals would have to be on the top of the roof, and that is an unlikely place to seek shelter.

The Phrase Finder says that this expression refers to “A narrow-minded or unprogressive person; one who lacks initiative. I’ve more often heard it used as a put down for someone who isn’t willing to take part in some activity because they think it might be unwise. I recall circumstances where I thought the “stick in the mud” was taking the responsible approach. Regardless, it originated with earlier versions of “stick in the briers, clay, mire, etc. that date back to the mid-1500s. Being stuck in mud was referenced twice in writing in 1733.