skykkjum

dat. pl. as adv., ganga s., to go rocking; gekk jörðin undir þeim s., the earth went rocking, under them, of an earthquake.

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adv., a dat. pl. [cp. Engl. shock], tremulously; varð landskjálpti mikill, gékk jörðin uudir þeim skykkjum, the earth went rocking under them, of an earthquake, Edda i. 144 (skukkum v. l.); svá gékk skykkjum (skrykkjum the Ed. 34) hallar-gólfit undir fótum honum sem bylgjur á sjó, Konr. (vellum MS.): akin to this is the mod. phrase, e-ð gengr skrykkjótt, qs. skykkjótt, it goes up and down, i. e. it is rather bad.