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1510s, "to carry over water," back-formation from obsolete wafter "convoy ship" (late 15c.), from Middle Dutch or Middle Low German wachter "a guard," from wachten "to guard," related to waken "rouse from sleep" (see wake (n.1)). The meaning "pass through air or space, float" is first attested 1704, and possibly shows some influence of northern dialect waff "cause to move to and fro" (1510s), a variant of wave. Related: Wafted; wafting.