[rdb3]

Agnosticism is the word for those who say "don't know". Atheisms claim to know.

Between the agnostic and atheist positions, the agnostic position is the most rational.

[Nicholas Conradin]

Between the agnostic and atheist positions, the agnostic position is the [more] rational.

I do not see how you come to that conclusion, unless you consider "reason" to possess some form of extra-sensory perception as would be needed if one were to allow for the existence of a god as a real entity.

"Agnostic" was a term made up by Thomas Huxley at the end of the 19th century. I suppose that it is a way for the irreligious to avoid being characterized (and condemned) as atheists, but IMHO that is a timorous concession to irrational superstition.