What is bus hold LOW or HIGH current refer to in the data sheet?
There's a taste of positive feedback (19uA typically) that allows you to leave unused data inputs floating. 

Sort of like this (but in the real chip the resistor would be more of a current source/sink formed by a couple of MOSFETs). 







simulate this circuit &ndash; Schematic created using CircuitLab

If the input was left open and not pulled high or low by the resistor (or current source) it could drift around and the gate might draw excessive current or it might create interfering EMI. Note that this does not add to the quiescent current draw. 

It's called "bus hold" because the last level that the input was forced to (high or low) is held (weakly).