From Middle High German beswæren (“to afflict, to depress, to annoy”), a merger from Old High German biswāren (“to depress, to burden”) (10th c.), from Proto-West Germanic *biswârijan; and Old High German biswārōn (“to burden”) (10th c.), from Proto-West Germanic *biswārōn. Related to swāren (“heavy”) (8th c.) whence schwer. The reflexive sense developed later in the 14th century from "to burden oneself", "to fret" to "to complain about something worrisome, burdensome". Cognate with Dutch bezwaren.