lewbʰ-eyo-
“to keep loving, desiring”love, believe, libido
Iterative of *lewbʰ- yielding English love, believe, Latin libīdō > libido.
Discussion
The PIE form *lewbʰ-eyo- (to keep loving, desiring) is an iterative derivative of *lewbʰ- (to care for, to desire, to love), with the *-eyo- suffix expressing ongoing or habitual action. The root produced one of the most emotionally charged word families in the Indo-European vocabulary, spanning romantic love, religious belief, and political freedom.
The Germanic branch preserves the root most transparently. English love (OE lufu, from PGmc *lubō) continues *lewbʰ- with the core meaning intact — making love one of the oldest and most conservatively inherited emotion words in English. German Liebe (love), Dutch liefde, and Gothic lubō confirm the pan-Germanic distribution.
The connection to belief is less obvious but etymologically secure. English believe (OE belȳfan, from PGmc *ga-laubijaną) derives from the same root: to believe is, literally, to hold dear, to love-as-true. German glauben (to believe) and Dutch geloven continue the same formation. The semantic chain from "love" to "believe" passes through "trust" — what you love, you trust; what you trust, you believe. This chain is preserved independently in Latin crēdere (to believe, from *ḱred-dʰeh₁-, "to place one's heart"), showing that the conceptual equation of emotional attachment with epistemic commitment is an ancient Indo-European pattern.
Latin libet/lubet (it pleases, it is desirable) and the derivative libīdō (desire, lust — whence English libido, Freud's term for psychic drive) continue the root in the Italic branch. The semantic narrowing from general desire to specifically sexual desire occurred in Latin itself; the PIE root carried no specifically sexual connotation.
The free/freedom connection enters through a different semantic path: PIE *lewbʰ- also yielded PGmc *frijaz (free, beloved — free as in "dear, belonging to the household"), from which English free, freedom, friend (OE frēond, "one who loves," the present participle of frēogan, "to love, to free"). The conceptual equation of love and freedom is striking: in the PIE and early Germanic world, to be free was to be among those one loves — the household, the kin-group. A free person was a loved person, a member of the beloved community. An enslaved person was, by definition, unloved — outside the circle of care.
Sanskrit lubhyati (he desires) and lobha- (desire, greed) preserve the Indo-Iranian reflex. Old Church Slavonic ljubiti (to love) and Russian ljubítʹ (to love) confirm the Balto-Slavic continuation.
The root's survival in love, believe, free, friend, and libido — five words that span the emotional, epistemic, political, social, and psychological vocabularies — makes *lewbʰ- one of the most conceptually far-reaching roots in the entire PIE lexicon.