means The faculty of deciding and intending — the mental power that lets you choose a course of action and commit to it (and also the legal document declaring what should happen to your stuff after you die).

from From Old English 'willa' (desire, wish) and the verb 'willan' (to want, to intend), rooted in a Proto-Germanic ancestor shared with German 'wollen' and woven through the Indo-European family alongside Latin 'velle' (to wish) — the same deep root behind 'voluntary' and 'volition.' The legal sense (a will and testament) grew from the same idea: it's literally a statement of what you want done.