The origins of phrase poker nuts are uncertain although it is thought to have come from old slang meaning 'delightful thing, practice or experience'. It is a 'delightful thing' of course, because in Texas Holdem poker nuts is best possible hand that you can have at any point in game.
If you have nuts, you cannot be beaten...at that point in hand. This is crucial factor that a lot of inexperienced players fail to take account of, nuts can move from one player to another and your hand which was nuts earlier on can end up being crushed!
The following example should demonstrate fickle nature of cards in Texas Holdem poker and how your nuts can quickly turn to pulp!
You are playing a hand of Texas Holdem poker and there are three players still in game at flop.
You get dealt 7 of clubs, 8 of diamonds; Amy has 5 of spades, 5 of clubs and John's hand is King, 9 of hearts.
The flop is dealt and cards are 9 of hearts, 6 of hearts and 5 of diamonds. This is a great flop for you - you’ve got poker nuts! At this point you have a straight - 5, 6, 7, 8, 9 - which cannot be beaten by any other combination of cards.
Now you decide to 'slow play' your hand and try to draw a bet from somebody with a high pair who will like this flop, so you simply check. Amy likes look of her hand now as she has flopped three 5s so she makes a bet which is called by John as he now has a pair of 9s with a King kicker. You like way it's going so you call bet.