The only free and comprehensive online etymological dictionary of the Spanish language
tocar (1) (Verb) "to touch"
13th cent. From Vulgar Latin *toccare "to touch," "to strike." From a West Germanic language (cf. Middle Dutch *tocken "to strike") or from Proto-West-Germanic *tokken "to push" but the route is unclear. Ultimately from Proto-Germanic *tukkan- 'id.' From Proto-Indo-European *du̯k-neh2- 'id.' From the root *deu̯k- "to pull" with an iterative stem.
Old Norse toga "to drag," Old High German zogōn "to pull," Middle Dutch tocken "to jerk," Old English togian "to tug" (English to tug)