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1690s, from some exclamation, possibly God's hooks (nails of the cross) or even God's hocks. Cf. godsookers (1670s). The use of Gad for God (cf. egad) is first attested 1590s. Among other similar phraseological combinations (all from 17c.) were gadsbobs, gadslid, and gadsniggers; in all of which the second elements are sometimes said to be mere fanciful syllables.