An Etymological Dictionary of the German Language/Helm
Helm (1.), m., ‘helmet,’ from the equiv. MidHG. and OHG. hëlm, m.; the same in OSax., OFris., and AS. (AS. hëlm, ‘helmet, protector,’ E. helm), OIc. hjalmr, Goth. hilms, ‘helmet’; a common Teut. str. noun, helma-, ‘helmet,’ from pre-Teut. kelmo-. Comp. OInd. çárman-, n., ‘protection’ (comp. the AS. meaning), with which the root kel in ModHG. hehlen, hüllen, is connected. Lith. szálmas, ‘helmet,’ and OSlov. šlěmŭ, ‘helmet,’ were borrowed at an early period from Teut.; so too the Rom. class — Ital. elmo (Fr. heaume), ‘helmet.’
Helm (2.), m. ‘tiller,’ ModHG. simply, from LG., whence a number of nautical terms found their way into HG. (see Boot, Kahn, Barke, Flagge, Spriet); comp. Du. helmstock, ‘tiller.’ E. helm, AS. helma, ‘rudder,’ Scand. hjálm, f., ‘tiller.’ In this case, as in most of the other nautical expressions, it cannot be decided in which division of the Saxon and Scand. group the technical term originated; as in other instances — see Boot, Bord — AS. contains the earliest record of the word. The MidHG. helm (see Hellebarte), ‘helve, handle,’ which occurs only once, and its variant halme, do not seem to be actually allied to the present term; they are connected with Halfter.