"It was the least I could do"

[Iomfats]

Why? Why didn't you do the *most* you could do? Why do the least? Where did this stupid phrase come from?

[sporty]

It probably came from the desire to be polite and is a modest way of saying you were glad to help. On the other hand, telling people that it was the 'most' you could do sounds like bragging - and it probably wasn't the most you could do anyway: that would entail giving them all your money, your house, your car, your family, etc etc. Don't thank me...it was the least I could do...

[braunp]

If you complete the expression with: considering what you have/she has/has been done for me -- it begins to make sense