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"cut off," 1510s, from Middle English loppe (n.) "small branches and twigs trimmed from trees" (early 15c.), of unknown origin. Related: Lopped (mid-15c.); lopping. Place name Loppedthorn is attested from 1287.
A language based on first-order logic.
["SETHEO - A High-Perormance Theorem Prover for First-Order Logic", Reinhold Letz et al, J Automated Reasoning 8(2):183-212 (1992)].