'Shania' is a term coined in poker forums to represent the balance in starting hand selection between playing profitable hands and playing too predictably. For example, in Hold'em 'AA' is the best hand. However, if the only hand a player would play UTG were 'AA,' over time observant opponents would notice this and punish the player. By playing only a 'profitable' hand, the Aces have actually become less profitable than they might be otherwise. The other extreme is just as bad, playing any hand. That strategy has complete deception, but too many negative value hands are played for such a strategy to be profitable.
Proper shania then is this balance between playing individually profitable hands and playing a wide enough range that your opponents do not gain an advantage over you. In some cases this may even mean playing some hands that would be considered unprofitable on their own, but that provide greater value to the rest of the hands by acting as deception.
The term is from the first name of country singer Shania Twain. See the forum posting below for more info: