Today it’s Mother's Day, which made me wonder if I could call G-d mother? Because G-d ‘gave life’ to all things. Of course we call him Aba, but why not Ima?
Why not? God calls us, Israel, His "mother":
Listen to Me, My people; and give ear to Me, O My mother... [Isaiah 51:4]
The Midrash adds how this struck bar Yochai as supremely significant:
[Rabbi Eleazar said:] The Holy One, blessed be He, first addressed Israel as “daughter” [then “sister”, then “mother”.] [As “daughter”,] in "Hearken, O daughter, consider and incline your ear…" [Ps. 45:11] As "sister” in "Open to me, my sister, my love, my dove, my undefiled... [Song of Songs 5:2] And when He loved Israel even more, He called them “mother”, for it says [see Isaiah, above]. Rabbi Shim’on bar Yohai arose and kissed [Rabbi Elazar] on his forehead [saying]... “If this had been the only thing I learned in life, I would have been satisfied.” [Exodus Rabbah 52:5]
These passages show that "mother" is a flexible appellation, not always literal. God has many masculine names, but also a feminine one, the Shechinah.
This seems to be a two-part question. Asking whether we can call G-d "mother," and why is G-d referred to as the father.
I read Jordan Peterson's book 12 rules for life. In the book, Peterson explained why many cultures, including the Bible, described G-d in masculine terms. He used the example of the Yin and Yang. The Yang is the masculine side, associated with light. The Yin is the feminine, negative dark side. Although women give birth men are seen as the giver of life, order. This is not anti-women, just the representations of dark and light in ancient cultures. The Bible does the same. Since G-d "spoke" order into the universe, He is described as masculine. We look up to the father. It is psychological.
Now that we know the origins and reasons for calling G-d Aba, we could call G-d Ima so long as we recognize that He is neither male nor female, “the Torah speaks in human language" (Rambam).
I do not claim to understand the following, I only quote what I’ve seen. In Sefer Sifsei Chein hakdama 9 he explains that the sefira of Bina is referred to in the zohar as אם and also corresponds to our foremother Leah. The sefira of Malchus corresponds to our foremother Rachel. Malchus gathers all of the influence from the higher sefiros and pours the shefa (influence) onto man manifesting the influence from above. Similarly a mother receives the seed of a man, cultivates it and manifests that influence to create a child.
So we see that some of G-d's attributes are referred to in the Zohar as אם and are associated with our אימהות. These are reasons to allow us to refer to G-d as אם.