This term occurs twice in Hariot, in adjacent paragraphs on pg. 754 in the section on useful resources. The term as Hariot uses it seems synonymous with “harvest” and is probably a variant of the word “offcome.” The OED defines as the product of multiplication in mathematics. Thus it seems that Hariot is waxing metaphoric here: the grain he is discussing ‘multiplies’ and yields its ‘product.’ - Matt