in psychology jargon, 1922, in Joan Riviere's translation of Freud, from combining form of libido (Latin genitive libidinis) + -al (1).
Entries linking to libidinal
libido n.
"psychic drive or energy, usually associated with sexual instinct," 1892, carried over untranslated in English edition of Krafft-Ebing's "Psychopathia Sexualis"; and used in 1909 in A.A. Brill's translation of Freud's "Selected Papers on Hysteria" (Freud's use of the term led to its popularity); from Latin libido, lubido "desire, eagerness, longing; inordinate desire, sensual passion, lust," from libere "to be pleasing, to please," from PIE root *leubh- "to care, desire, love" (source also of love).
-al 1
suffix forming adjectives from nouns or other adjectives, "of, like, related to, pertaining to," Middle English -al, -el, from French or directly from Latin -alis (see -al (2)).