Q: I swear, Google has 126mil for "I second that motion" but also 36 mil for "I second that notion" I have heard it both ways.. Example: Someone says "I want a cream pie!" I say "I second that notion!" OR would I say "I second that motion!" I mean what the hell??? THEY ARE BOTH FITTING!!!
A: In the context you cite, it would be "notion" since the speaker is expressing an idea or a wish. In the context of a meeting where somebody has moved a motion and you wish to second it, the correct word would be "motion".