Anima is a feminine Latin noun for "spirit, soul, breath". Ancient Romans believed that one's anima was in the chest - it was one's feelings, the breath et cetera. Therefore, when a person died, the breath (soul) escaped. Anima was related to feelings and heart; the counter part (masculine) animus was the logic and brain.

Obviously, the relationship between Seymour and his mother was emotionally powerful, and her loss triggered a turn of events for all of Spira in how it affected Seymour.