Allow us, if you will, to volunteer our knowledge about "velleity." It is a derivative of the New Latin noun velleitas, from the Latin verb velle, meaning "to wish or will." You might also wish to know that "velle" is the word that gave us "voluntary" (by way of Anglo-French voluntarie and Latin voluntarius) and "volunteer" (by way of French voluntaire). While both of those words might imply a wish to do something (specifically, to offer one's help) and the will to act upon it, the less common "velleity" refers to a wish or inclination that is so insignificant that a person feels little or no compulsion to act.
Word History
Etymology
borrowed from Medieval Latin velleitāat-, velleitās, from Latin velle "to want, will" + -itāt, -itās-ity — more at will entry 1