geek · noun, verb1
Started as carnival slang, likely from the British dialectal term geck (“a fool, dupe, simpleton”) (1510s), apparently from Dutch gek or Low German geck, from an imitative verb found in North Sea Germanic and Scandinavian meaning "to croak, cackle," and also "to mock, cheat" (Dutch gekken, German gecken, Danish gække, Norwegian gakke, Swedish gäcka). The root still survives in the Dutch adjective noun gek (“crazy" or "crazy person”). Compare gink and also Old Norse gikkr (“a pert, rude person; jester; fool”).
geek · noun, verb2
Probably related to keek. Compare German gucken (“look”), kieken (“look”) and the dialectal corruption of Dutch keek (“keek”) (from kijk (“look”)), kijken (“to look”). Australian use from Cornish dialect.
Etymology from Wiktionary, CC BY-SA 4.0.