terp-eyo-
“to satisfy, delight, turn toward”torpedo, torpid, entropy
Iterative of *terp- giving Latin torpēre > torpedo, torpid; Greek trepein related to entropy.
Discussion
The Proto-Indo-European root *terp-, reconstructed by Rix in the Lexikon der indogermanischen Verben as *terp- with the core meaning "to satisfy, to fill with contentment," generated a causative-iterative formation *terp-eyo- that carried the sense of bringing someone to a state of satiation or delight. Pokorny (IEW 1077) groups the reflexes under *terp-, *trep- and emphasizes the semantic range running from pleasure through satiety to its eventual exhaustion. The Greek evidence is the most transparent: térpein means to delight or gladden, and the noun térpsis denotes enjoyment or pleasure, preserving the root's original positive valence with little distortion. Homer uses the verb freely of the pleasures of feasting, song, and rest, always with the implication that some appetite is being genuinely fulfilled. The Latin development tells a more unexpected story. Torpēre, meaning to be stiff, numb, or sluggish, appears at first glance unrelated to delight, but the semantic path runs through the concept of oversatisfaction — the torpor that follows excess, the heaviness after a feast, the stupefaction of one who has had too much of a good thing. Watkins traces this progression explicitly, noting that the shift from pleasure to numbness is psychologically coherent and paralleled in other language families. From torpēre English inherits torpedo, originally the electric ray whose sting produces numbness, and torpid, describing the sluggish state of hibernating animals or languid minds.