Meaning

noun the time at which something is supposed to begin

noun a compensating equivalent

noun a horizontal branch from the base of plant that produces new plants from buds at its tips

originFrom off- + set, used to construct the noun form of the verb to set off. Compare Middle English ofsetten (“to encumber, harass, beset, besiege”), from Old English ofsettan (“to press, oppress, overwhelm, crush”).

Etymology from Wiktionary, CC BY-SA 3.0