"House Hold" (or Hold Percentage) is the measure of the amount of money a casino table game keeps from the total amount of money that is dropped into the table game's cash box. The term is closely related and correlated to House Edge, but the terms are not the same. The differences between "House Edge" and "House Hold" are understood by very few people -- even those in the gaming industry.
The "house hold" is normally calculated for a table game after each shift or at least once a day. Descrepencies in the house hold from the typical amounts can lead to further investigation into possible cheating. The "house edge" for a particular bet remains constant while "house hold" can vary greatly from day to day based on random chance, player whims, and other factors. For most table games though the house hold will average out over time to a figure between 15% and 35%.
Some people also use the term House Hold to refer to a slot machine's Hold, but more often when discussing the Slot Hold the casino talks about its Payout Percentage. Typical Slot Hold is between 2% and 8% in the U.S. which means the Payout Percentage is approximately 92%-98%
To calculate the House Hold we take the total amount of money won by the casino at the game. We divide this amount by the total amount of money that is dropped into the box at the same game in the same time period.
Lets calculate the hold over a one hour period: a Black Jack table starts with $5,000 in chips in its rack. The players coming to the table buy $2000 in chips. At the end of the hour the casino has $3300 in chips in its rack and $2000 in hard currency in its drop box. The casino has won $300. The House Hold for this time period is thus $300/$2000 or 15%.
Even though the house edge in most casino table games is between 1% and 5% the house hold for each of the games is typically between 15% and 50%. This increasing hold comes as the players stay longer and longer recycling their same money through the same terrible games with negative expectation. If the casino can convince you to stay longer (by offering incentives or good service) they can increase their hold. They can also increase their hold by speeding up the games as much as possible.
Another example: in Craps the house edge is only 1.414% for a pass line better. So for each $10 bet you place you can expect to lose $.14. You buy into the game for $100. If you stick around playing craps for ~100 rolls you can expect to have around $86 left. If you stay for ~200 rolls you can expect to have only $72 left. So even though the house edge was a measly 1.4% the casino managed to take between 14% and 28% of your money.
Games that have greater house edge also tend to have greater house hold, but there isn't a one-to-one correlation. If the players aren't "having fun" or the game is particularly slow moving or if the game is perceived to be too hard then players will pick up their chips and take them to a different table or worse yet (for the casino) they will cash them out and leave.