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The origins of this idiom.
The meaning of this phrase.
Phrases and Idioms - The Meanings and Origins For Many Common Idioms and Phrases
Often said in poker when someone has a winning hand, as the others 'weep' over
their loss. The expression can also refer to things that may cause distress to others.
* Well, would you look at that; read 'em and weep fellas, because I have a royal flush!
Note: The origins for most idioms are unclear. Often times, the origins you see listed are plausible theories to how an idiom came to be, but not necessarily so. The quotes you see that contain the phrase are the oldest that I could find, but it's very possible there are older recordings somewhere, so if you know of any, let me know!

Keep in mind, just because you see a saying in a newspaper from 1850 does not mean it originated in that year, or from that newspaper. In all likelihood, if a saying is already being used in a form of media like that, it's probably from an earlier time. The purpose of these old quotes is to show, with proof, how old some phrases go back in history.
Title pic for the expression Read Them and Weep.
Cards used to play various card games, like poker.
This phrase is believed to come from a popular card game known as poker. Poker is a
game where players put together different combinations of cards that are worth a set
amount of points. Certain arrangments of cards are worth more points than others, hence,
during the game, players attempt to build the strongest combination of cards possible before the game is over. At the end, players reveal their cards to each other and whoever has the strongest set of cards wins.

Sometimes, betting is involved in poker, which makes losing more painful. Players who are feeling extremely confident with the hand they have might decide to place the cards on the table for others to see, and say something along the lines of 'read them and weep.' The confident player is essentially saying: "Read my cards and be sad, because I've won and you've lost."

Today the expression is used not just in card games, but for anything that may cause discomfort to another person. The earliest written form of the phrase I could find is only from the past century or so. For example, the expression is used in The San Antonio Evening News, printed in July 1919. The term is used under the Sports News section of the newspaper:

"With the exception of one or two close decisions, Umpires Lewis and Schaffer did faily good work,
probably because they had been made very good 'boys' by the irate fans . . . Few arguments were
indulged in with the arbiters. Read 'em and weep!"

Something interesting to note: Around the same time, in 1919, several newspapers used the idiom right before presenting a list of items for sale. The implication was that they probably expected customers to "weep" with joy after seeing their cheap prices.
Know Your Phrase -  An Alphabetical List of Common Phrases, Sayings and Idioms With Their Meanings and Origins > R-Letter Expressions