O.E. nearu, from W.Gmc. *narwaz (cf. Fris. nar, O.S. naro, M.Du. nare), not found in other Gmc. languages and of unknown origin. The verb is O.E. nearwian, from the adj. Narrowly "only by a little" is attested from 1550s. Narrow-gauge railway is 4 feet 8.5 inches or less. The narrow seas (c.1400) were the waters between Great Britain and the continent and Ireland.
Unification followed by unfolding. The left-hand side of a rule is unified with some term, resulting in a set of variable bindings. The term is then replaced by the right-hand side of the rule with values substituted for bound variables.