late 13c., from Old French torche, originally "twisted thing," hence "torch formed of twisted tow dipped in wax," probably from Vulgar Latin *torca, alteration of Late Latin torqua, variant of classical Latin torques "collar of twisted metal," from torquere "to twist" (see thwart). In Britain, also applied to the battery-driven version (in U.S., flashlight). Torch song is 1927 ("My Melancholy Baby," performed by Tommy Lyman, is said to have been the first so called), from carry a torch "suffer an unrequited love" (also 1927), an obscure notion from Broadway slang.
"set fire to," 1931, from torch (n.). Related: Torched; torching.
To be infatuated with: “Frank may be engaged to Helen, but I think he still carries a torch for Laura.”