An Etymological Dictionary of the German Language/drohen
drohen, vb., ‘threaten,’ from the equiv. MidHG. drôu, wk. vb., which is the denominative of an earlier dro, f., ‘threat.’ The more ancient vb. is ModHG. dräuen, from MidHG. dröuwen, drouwen, OHG. dręwen, drouwen; Goth. *þraujan, AS. þreán þreáde) (equiv. to E. to threaten). OHG. drô, drôa (gen. drawa), corresponds to AS. þreá; Goth. þrawa is wanting, gen. þrawôs, f., ‘threat.’ In E. the word is obsolete. Beyond Teut. there are no cognates.