Know, that just as we described, with each and every world there are five partzufim ("faces"), [which are] Arich Anpin, Abba, Imma, and Zeir Anpin. And in each of these, there are the five types of souls of a person, and going from lowest to highest, they are Nefesh, Ruach, Neshama, Chaya, and Yechida. Here, the Nefesh is from Nukveh d'Zeir Anpin; the Ruach is from Zeir Anpin; the Neshama is from Imma; the Chaya is from Abba which is Chochma (wisdom), because Chochma is the place of life in the secret of "והחכמה תחיה בעליה".
And the Yechida is from Abba and Imma which are called Keter because it is alone and unified, because, unlike all the other Sefirot, it does not have a female counterpart, just as we know from the passuk "ראו עתה כי אני אני הוא," as is explained in Sefer haZohar, Parshas Bereishis.